http://chronicle.com/forums/index.php/topic,60567.0.html this thread might give you some idea of the career problems it may cause.
As to living part-time in London, it is going to be complicated (and I bet your tax situation is going to be complicated too - hope research site is a location with a double taxation agreement...). If you look on Gumtree you can find short-term accommodation ads
http://www.gumtree.com/london/london-short-term-houses-for-rent_211_1.html but I really doubt you'll get a bargain. The only person I know who managed something similar in a halfway financially affordable way rented a colleague's spare room as an informal lodger. It only worked because they were friendly and the colleague was struggling with his mortgage so cash-in-hand was helpful. It might be worth e-mailing round to see if anyone in your department knows of anything like this, that might be arranged.