I really think you should look at wider issues than schools when deciding where to live. Rural Gloucestershire is very different from Tunbridge Wells; and not just in schooling. You speak of Chipping Campden, which is lovely, but a long journey from all the grammar schools here - the nearest would be Pate's in Cheltenham, which would take close on an hour at the very best of times, which mornings are not likely to be. Pate's is one of the hardest schools to get into in the entire country (and it might not suit everyone either), so you might be looking at the the Gloucester (single-sex - again not everyone's cup of tea) grammars, which would take even longer, or Stroud - longer still. I am not sure about public/school buses from outlying areas either - a friend in Winchcombe has to drive her DC to Cheltenham Racecourse (20 minutes) in time for a 7.30 bus to Gloucester. Gloucestershire is super-selective - around 5% of children get into grammar, which I think compares unfavourably with Kent. Selection is by VR only and is extremely competitive - many of the private schools start teaching VR in Year 2 or 3 and the parents buy in private coaching on top. It is almost unheard of for an un-coached child to get into GS here, though I have heard of one child this year who has.
Cotswold School is not especially highly regarded but has outperformed some of the GSs this year in A level results. No idea about CC. Most of the secondary schools here are very good, and their fortunes wax and wane in cycle, it seems. Because the grammars are so very selective, the standards in the non-selective schools, especially but not exclusively in the north of the county, are generally very high. Quite a lot of people in rural areas don't even try for GS, for logistical or ideological reasons, so there are very bright children in the catchment schools - a friend of mine's daughter has just got a clean sweep of A*s from one. It is very easy to get caught up in the rather overboiled GS culture here and overlook the other possibilities, though if you are out in Blockley or somewhere you would be less likely to encounter it. Of the 2 primary schools you mention, I know a bit about St James and Ebrington as I know a member of staff there: it is 2 federated tiny schools and seems a very happy place, with good results as you would expect. If you are looking for a small village school I imagine it is fine. There are also good bigger ones - again, depends on your taste and what you value in a school. One of the 'best' primary schools, results-wise, here, is one I would not have sent my own children to under any circumstances; others probably feel the same about the school I chose for mine. Horses for courses, and all very personal - it has to 'feel' right to you and your child.
Be aware that once you get over the border into Worcestershire the system is different, with first and middle schools still the norm. A bit further and into Warwickshire and you are back with superselectives, though a totally different selection package and I think a tiny incy wincy bit easier to get into on account of more places per head of population(may be wrong on this). People do come from London, Bath, Wales to try and get their children into the Gloucestershire grammars
I really do think it comes down to lifestyle though and what you want in other aspects of life. Personally I wouldn't have moved here for the schools alone - definitely not that much of a pull. You need to come and spend time here and ask if you like the area (and it is beautiful) and all it has to offer, better than your alternatives. It is very early to think of secondary before your daughter has even started primary - so much could change, with academies, changes of government etc.
Hope this helps.