I used to hop between ISP's all the while but I have been with my current one for over a year which is some going for me. I would highly recommend them... Entanet is the wholesale provider and any of their resellers are very good.
I use UKFSN. The only downer is their shit website
UK Free Software Network which may put people off. Another reseller of Entanet I have experience of is ADSL24
ADSL24 Broadband - Home
£20 per month and 30gb peak and 300gb offpeak suits me very nicely.