Business people that look at the rankings will see Bath and Imperial as global top 100 schools. Bath in fact is one, if not the, most established MBA courses in the UK. The whole environment is priceless. It performs consistently well regardless of the year.
Imperial is clearly another top school and their strengths in disciplines like science and technology also help them to compete with the best business courses, as does it's proximity to the business world in London.
An MBA is a valuable career investment that needs adequate funding until you realise the returns, so the most expensive is not necessarily the best. However neither central London nor the centres of Bath are really cheap places to live, particularly off-campus. Have you thought about earning fees whilst on the course? This can be achieved at schools like Bath, through an external consultancy project, even if you are self-funded initially. This is possibly easier to achieve now than it was in the downturn. Whatever you decide keep an open mind - useful as they are, many people in the business world are in fact less focussed on the rankings than many politicians may have you think. The best choice is the choice that is right for you. Thanks for asking us!