I followed Alan Parson's instructions and they were perfect!
I bought a new clock online from buyspares.co.uk for £39.80 inc VAT and postage, without checking serial numbers, and dismantled according to Alan's instructions.
However when I got the old clock out, the connectors were in a different place to the new one. I phoned buyspares who checked serial numbers and said that I needed a different one, at £110.
I called Rangemaster Technical support (buyspares gave me the number) and they were very helpful. They said they were interchangeable, and that the 2 cables going to the white box (you will know what this means when you have the clock in your hand) should be connected the same, and the cables going to the other 2, (marked L and N on the old clock) should be connected to the 2 large connectors at the bottom of the new clock. Surprisingly, it makes no difference which way round, even though they are live and neutral. (there are also 2 smaller terminals on the new clock which are not used on the Leisure 110)
Tech support told me that the buttons on the new one required slightly different operation to set the clock, but I was able to download a manual from http://www.rangemaster.co.uk/range-cooking/rangemaster-110.aspx
We now have a cooker in perfect working condition again, thanks Alan!
PS, my blue wires were already connected together on the same terminal, so that quick fix would not have worked for me.
All in I spent a little over 2 hours doing this, but Alan's estimate of an hour would have been fine if I hadn't had to spend so long on the phone and internet. I also took a fair amount of time cleaning, you will be surprised at what collects behind an oven over the years!
Geoff Nicholls, March 2011