Hello Adam. I too have noticed a decline in numbers of hedgehogs in my garden this year, although I think the shrinking numbers started last year.I was away for ten days on holiday, and upon my return the number of hedgehog visitors had dropped dramatically. I can only surmise it was because their usual plentiful supply of food, courtesy of myself, was no longer available. This year, although numbers were well down, when I went on holiday in September I asked my nextdoor neighbour to feed them in my absence. This seemed to work and I hope that they have all have gained enough weight to see them through their hibernation.
Beaverscout