History degree without History A-Level?

A lot of the time Highly recommended is definitely a push for you to do it. I mean doing a university degree is a big step up from A level but I think doing the subject at A2 will at least prepare you for it.
A level history is far different to GCSE so I would say do it. It gives you new skills that would be useful in Uni.
Plus since you're planning on applying to very competitive unis it's probably more likely that you get consideration with a good A level grade in the subject because it proves that you can do it.
However untimately it's up to you. I can see that your planning to do more than the necessary 4 subjects which means you will already have a lot on your plate but the fact is if you're really interested in the subject you either have to study it or prove it through other areas. That means if you don't do it at A level you have to show your interest in history through other subjects or extra things outside of the curriculum.

Hope that helps,
Nemo

Swap it for English Lit, it may be only 'highly recommended' rather than a requirement but there is no point disadvantaging yourself. Given the choice between you and another candidate of similar capabilities but with history A-level, the guy with history will be taken 99/100 times.

So you think it's worth keeping the maths and science side instead?

If you're considering doing History at uni, why are you studying FM? Seems like the best thing to do would be to drop it and replace it with History. Are you planning on doing Physics/maths at uni?

If you want to do History then doing it at A-level is basically essential even if unis don't actually say it. Otherwise, you can do anything you want. If you want to do History with something like French or English then doing those would be a good idea as well. Maths is good with literally anything so do it and if you are capable of doing further, then it can only help you to do it. But from the subjects you are considering, then Maths, FM, Physics, French/English and History give you the most rounded combination. Personally I do Maths, Politics and History (dropped Economics after AS.)

I'm doing my A2s in Maths, Politics and History and am looking to do Politics and History at university, already submitted my application and received some offers.

I have no clue. If you're adamant you don't want to do it at A level You should go see what your school/college offers for enrichment. Or you could try out an online course; however, if you do that then you have to remember its even more work. I know it looks good to do extra AS levels but at the end of the day if its going to stress you out and you end up doing well but not your best, is it really worth it? It's all down to how much you can handle.
But if this was me I'd either drop the maths or the physics and do the history a level. If your not going to pursue the other two, you're better off doing the subject you want to continue. It'll definitely give you a better chance of getting in to the Uni.