Stuart
I don't know Newbury or London for herbs etc.
However if you have to shop at a supermarket, Waitrose is the best of the nationals, with Marks and Spencer 2nd (IMO of course). Most now sell mainstream herbs (basil, sage, parsley etc) growing in pots. Other herbs can be got in pots from garden centres. Wider selections of dried herbs are available in supermarkets.
try
http://www.yell.co.uk for specialist food shops (it's the comprehensive yellow pages/commercial listing and many have websites). Look under Newbury and/or berkshire and speciality or ethnic food shops.
Meat is pretty poor quality here (I guess you know that), but if you can get a local recommendation of a good butcher, then good stuff can be found. Likewise a greengrocer is worth taking on recommendation.
Best of luck!
Ian