I guess you've taken nice a step up in your weekly take home pay, I had something similar when I started flying, ended up with an extra €100 in my pocket at the end of the week. I decided that I'd spend that on flying, I had gotten used to living on the lower pay so just continued with the same lifestyle plus the flying.
Is there any cheaper options than £150/hr, I flew the Tecnam P2002 which is a fine airplane and on average cost me £85/hr. I'd recommend a flying club rather than a school, generally a lot cheaper and a nicer environment.