I've just been talking to a helpful lady at jobcentreplus about this and thought I'd update you in case anybody else finds themselves in the same situation. Apparently if you have claimed Income Related ESA in the past and been switched to Contribution based ESA, then you DO still have an obligation to inform DWP if your savings increase by more than £250 at any point and the DWP will still contact you once a year and insist on seeing all your bank statements. The lady could not give me a reason for this, just that it is standard practice if you have claimed Income Related ESA in the past.
The following user(s) said Thank You: s.jmoore@blueyonder.co.uk, Gordon