Tailscrape, after completing your initial flying training and achieving your ATPL, why not make yourself more marketable by getting a type rating. I understand the financial aspect, however it would make more sense to get a 737 rating, rather than join the ranks of low paid flying instructors unable to make a living. Yes it's a gamble, but so is investing £35000 in your future career anyway. Ideally we would all like to join the BA cadetship, but alas, this isn't always achievable.
To answer the question posed initially: 737 or 320 would do the trick. Rgds.