I signed up this afternoon for the Equifax 30 day free trial credit report.
It's completely free for 30 days as long as you remember to cancel before the 30 days are up (otherwise it's £6.99 a month). It does not affect you credit rating by signing up. There's also £20 Topcashback available and mine has already tracked!
I've posted this in the deals section as you do need to submit your bank card details (although as I say no money will be taken until after 30 days). It's also possible some people might like the service and choose to stick with it.