"I really think I should try to find more Sidders time this year - but I have the problems of an elderly dog who needs dogsitters and a one-man practice with clients..."

That is a problem. In Buenos Aires' Plaza San Martin, which is a park near the city centre, there is an area where folks leave their dogs with a band of dog carers whilst at work or maybe just shopping. I tried counting them once and gave up at 100! My point is that maybe some enterprising people could arrange something like this for Sidmouth or even other festivals.