What are people’s thoughts on the Bob Martin Spot On treatment for Ticks and Fleas.Local gamekeeper swears by it however gets very dodgy reviews.

I have read about too mamy nasty reactions and my personal.chiice in the very rare occasion I need to use these things is to buy from the vet .I hate using  them and will only do so if we have parasites

At best it is completely ineffective.

Use an approved and modern veterinary tick preventative, not Bob Martin.

I'd never use Bob Martin. When I used them years ago for other animals there was always problems. the small rodent one both times some mice died, when I used the ones for rabbits my rabbits neck swelled up, a friend used it on her guinea pigs and one fitted and died. The vet at college said to us that the reason some spot ons are sold in shops and not vets is because if they cause too many reactions vets won't sell them.
A friend's mate use to use them for their dogs and they always had fleas.

personally wouldn't use, recently seen a picture of an awful reaction looking like a large burn.

Aside from potential reactions, I'd not bother because I have yet to meet a dog for whom it's actually worked!  The gamekeeper may be thinking it does because the dogs don't have fleas, but are they actually getting them in the first place?  Mine never do unless one particular dog brings them in when he comes for grooming and since the owners got their final warning for it (incidentally they have used BM stuff too, it never touched the fleas), he's been on Bravecto and my dogs have been flea-free.  So potentially, I could have been using BM spot ons in that time in the belief that they were working!