I've just bounced British Gas, having had too many problems - too many to mention. Customer service is terrible, but polite! At one point I had three different issues being (not) resolved - broken smartmeter, imposition of an exit penalty on a new tariff I hadn't consented to, and their insistence that I was receiving a supply of electricity at one address and gas at another! They had to go.
I switched to SSE/Marks and Spencers to save £80 a year, fixed until Sept 2014, just in time before the price rises start in November. Made it by the skin of my teeth. They announced the 8.2% rise the day after my contract began!