I don't know Manchester, Birmingham (or Leicester), but I have to say that there is probably nowhere else in the UK that offers the range of activities,opportunities, and diversity of London. The problem, as you say, is the high cost of finding somewhere to live here.
Of course, you don't have to share with Spanish girls! Why don't you look for a flatshare (or house share) with a more mixed group. That would introduce you to a wider social circle. If you focus on south and east London, you will find costs are slightly lower, although some travelling may be necessary - another of the drawbacks of living in London.
You will probably have to make a trade off between cost of living and lifestyle. It's not an easy one to call.