An online survey by Opinium for comparison site Moneysupermarket.com in February 2010 showed that, disappointingly, of people requesting a MAC to enable them to change their broadband provider 34% experienced delays, which could cost broadband internet users as much as £143 a year. 82% of broadband users didn't change provider in the past 12 months.
It does pay to shop around. UK comms regulator Ofcom have recently accredited Broadband.co.uk for its broadband internet price comparison calculator, under a scheme launched by Ofcom because Ofcom had found that 65% of internet users would be more likely to shop around if they had information to calculate the cheapest supplier based on usage, with 66% being more likely to trust an accredited price comparison website. See Ofcom's consumer FAQ.
Not many websites have been accredited by Ofcom so far - the others include BillMonitor (for mobile services) and SimplifyDigital (for digital TV, landline and broadband services). Oddly, Moneysupermarket.com themselves don't seem to be accredited yet.
It used to be a nightmare to switch providers and Ofcom kept an eye on things for a while with their Own-initiative enforcement programme to give effect to General Condition 22 (Service Migrations), even fining Prodigy, but unfortunately in November 2009 they stopped as they thought things had improved enough.
Personally, while I have a lot of time for Ofcom, I think they shouldn't have stopped monitoring migrations, and the recent Moneysupermarket survey seems to confirm my view. Ofcom's light rap on the knuckles to Pipex was too lenient given the way Pipex had deliberately treated customers who tried to leave (I was one of them, Pipex told me they'd treated my request for a MAC as a notice to terminate my broadband service completely, not to switch! - and others had even worse experiences than me, just check out some of the transcripts of phone calls with Pipex in the Ofcom Pipex notification.)
See also How to switch your DSL broadband ISP: easier procedures, with teeth for Ofcom, and Ofcom's webpage and video, below, on how to choose the right ISP deal, and consider complaining to Ofcom if you have problems switching:
I think more still needs to be done by Ofcom to protect consumers. I am planning to change ISPs but I don't dare to do it yet because I can't afford for something to go wrong with the switch these next few months. I'm only going to ask for my MAC in June or July as I can survive if an attempted switch goes pear-shaped in August, but I can't risk the migration going wrong in the near future as I absolutely need working internet at home.