IS firms sound like dystopian sci fi. Perhaps the money's ok. 

Sell a few of those heads in the fridge.

sounds like the US firm might be solving that problem for you soon anyway...

in-house - yes possible but will be a big hit on pay, but you will def have improvement in WLB and probably better options for moving away from legal practice. 

civil service - even bigger hit on pay, working in the opaque government machine and constant public attacks from the press and government ministers. if you can put up with that fine and WLB should be v good, but pay will be rubbish, at least by London legal standards (i did a secondment to the GLS a few years ago and most of the lawyers were either v much the "second salary" in their marriage and had a spouse earning a lot more, young 'uns just starting out or activist types for whom money is a bit dirty anyway). 

You definitely don’t want to work for an IS firm.

Don’t move in-house too soon. If you trained at your current US firm, stick it out for a couple of years trying to focus on building your skill set and your contacts rather than chasing hours and bonuses, and don’t acquire an expensive lifestyle.

Then try staying in PP but moving to a mid tier City firm and gravitating towards commercial as well as corporate stuff before moving in house at a decent level of seniority if you still think the job is demanding too much.

If you moved on qualification, give it an extra year or so before moving.

I have worked at a few different firms, and there are some where you can have an OK life, even in mainstream corporate. Definitely harder to achieve in MC and US than in other City firms.

What TT said. 

dont go too soon dont go too late.

dont ever work civil sevice other than as a paid retirement gig

Alternative to in house would be big 4. Similar culture; get to be a pretend proper lawyer; can maybe segue into being a talking head of crypto stable ai coin or something down the line

wait for them to fire you. Quiet quit in the meantime. Youve probably got around 6 months plus the 3 + 3 pay thatll take you through until this time next years.  Then you'll be a brighter prospect for an inhouse role (but expect to be on £70k). 

resign, do a few month course to retrain in software development, start a startup, be an agent of the future not a pawn of the gerontocracy

Head to a nice civilised firm in somewhere like Holborn.  You'll be paid rather less but still well compared to most people and you'll also do rather less work and generally be treated like a human being by pleasant colleagues.

Don't join GLS.  Awful pay.

If you fancy that sort of thing, try one of the non-GLS government jobs e.g. ofcom.

You can go in house early if you like.  Depending on where you go, PQE is much less important.  Also because seniority is role-specific, not PQE based, you can get on by moving jobs.

To be frank, you don't sound like you have what it takes to work at any sort of serious firm or ftse100 corporate.  Pull yourself together and put some years in at the coal face or resign yourself to an inconsequential job somewhere that matches your appetite for work  

It's a lot to give up the whole thing after all the years of training so think about if it's the actual profession rather than working at a firm/ doing dull/ work the hours..beairng in mind that most jobs (whether it's law, finance, PR, marketing, HR,) all mostly involve being at a computer for hours!!

Ignore all those who say you cant go inhouse early. It's rubbish. Lots of people do these days and there are some very well paid inhouse jobs in your area. If you choose a company carefully you can be doing standard working hours with a good work life balance and pick up your interests, friends etc.

I think lots of people burn out/ leave law because they hate the firm/ hours but it does not have to be like that if you move. Look at everyone on her e- wouldnt have time to rof if they were doing corporate hours!!

Also the GLS if pretty much the opposite in terms of pay if you're used to corporate rates so a huge huge difference. Most companies will ofer somewhere between the GLS rates and law firm rates. Don't expect to necessarily match the law firm rates (many of which are now paying juniors more than senior lawyers inhouse with over 10 years PQE) but if youre not just driven by earning a huge salary then inhouse is a great options. Then if you still hate it you know it's not just the firm. Hope that helps!!

Lol Warren, I work for a ftse100 and let me assure you it is full of utter deadwood.

Honestly it sounds to me like you've got a healthy perspective.  You're bang on about the delusional character of many PP lawyers who seem to think they are adding enormous value when they are usually doing the opposite.

Go inhouse in a few years and then eventually move away from law altogether if you want.

I skipped inhouse as I was desperate to get out of legal and took a commercial management type role (where legal stuff was useful for sure).  Decent pay cut of course. Once you are out of legal, the world is your oyster - people stop putting you in a stupid little box and it is much easier to move into new areas.  

Kudos to the OP for figuring out quite early what it took me 6 years at Kirkland to figure out. My advice, which has mostly already been said above, is:

1) Wait for them to manage you out. They will, eventually, and in the meantime every month on that salary is a wonderous thing.

2) MOST IMPORTANTLY - do not get addicted to the salary. Immediately upon receipt, transfer it to a different account and make like you're still on the trainee salary.

3) You can go in house early, but bear in mind you won't be a proper lawyer yet and you should make sure that your new shop has someone who can teach you. I'm now IH and last year we hired someone who was a refugee from a US firm and it didn't work out well. He basically knew nothing at all and lasted about 9 months before he quit to leave the law entirely. In hindsight, we hired too junior and I'm now putting a floor of (say) 3 PQE on our searches so we get someone who has at least proved themselves in PP.