A friend of mine with an OES is looking to visit the Cotswolds for a short break with their caravan and
was looking for any reccommendations of dog friendly places, scenic walks, pubs and most
importantly a highly rated flat campsite suitable for caravans within the cotswolds.

Does anyone have any suggestions/reccomendations please?

There are lots of Caravan Club sites of a high standard in the Cotswolds.  Dogs are welcomed on all of them and usually there is a dog walk on or near the site.  Check on their website, I am sure that you will find somewhere suitable.  :)

Camping and caravan club site at winchcombe is lovely. Public footpath adjacent to site crosses open agricultural land. Some lovey walks around winchcombe, snow hill, naunton, stow on wold & slaughters -  Worth investing in pathfinder Cotswold walks ( available on amazon)  Some super pubs local, lots have beer gardens with a map you can even plan a walk around a pub lunch :)

if they like animals they could visit Cotswold wildlife park and gardens, dogs are allowed in on leads, they cant go indoor so cant go in the bat room and reptile house, and cant go in the lemur walk and kids petting farm as they have free ranging animals.
http://www.cotswoldwildlifepark.co.uk/plan-your-visit/facilities.htm

That is just down the road from us and we have a lovely dog friendly pub that does lovely food.

http://www.shiptonlamb.co.uk/