Denham will want you to fill in a GAR form. You can find a blank one in Word format here.
Actually that is quite a good point. The tower got very flustered recently when they received my flight plan but had not seen a GAR form (I had already sent it to SB the night before). I am not sure how many airfields do this but Denham have a policy that the tower needs to see a copy. To be fair they will then do all the legwork of co-ordination with SB for you.. Especially since Thames Valley SB keep changing their phone numbers (they moved upstairs and did not move the phone lines)
Otherwise Fly as Fly Stimulator and others have said - it is a very pleasant Journey.
PS. I always tend to talk to Elstree and Stapleford when I fly very close to them. Otherwise Farnborough should be good to use. The last few times I have always been handed to L2K directly (by London) but have the Lille Freq to hand just in case.