research councils pay something like ~12K outside london and ~14k within, thats tax free, and you get your council tax paid as well. its the equivelent of about £20k per year paid employment. therefore about the same as teaching starting off...but the clincher is that PGCEs now cost you to do at 3K fees and you can take a loan on that, so in effect the 1st year of teaching you will be less off than doing the same as phd. The thing is teaching rises about a k a year for first 5yrs, so 6 years after starting PGCE you are looking at 26-27k with inflation where as a postdoc (in my area of research anyways) will be looking at max £24K after 6 yrs from starting phd. plus in teaching you can get your SEN and management points to boot, so 5 years after teaching you could be on £30K quite easily ( a mate of mine is 3 years out of PGCE and is already a head of dept earning over 30k b&stard).
Depends what you want in life, research interupted by having to teach spoilt, hung-over, arrogant 18-21 year olds or babysitting and hitting govt targets.