Need a tour for 1 full day trip from London to Cotworld.

From where? London, or somewhere else? By CotWorld, do you mean the Cotswold Hills? If you say Cot World to an English(wo)man they wonder if you are looking for a large store selling baby products.

The Cotswolds is a large area northwest of London - a couple of hours away.

I have heard decent things about Evan Evans tours.

We used Gray Line Tours for our day trip to the Cotswold's. Gray Line.com lists the tours they offer, They subcontract their tours to Evan Evans in London. We totally enjoyed all our day tours.

Depending on what you want to do and when you want to do it, you might want to check out London Walks. They probably still run a tour (train, walk, bus, walk, train) a couple of times a week. Read the fine print, however....it was more expensive than we expected, once all the transportation was added in (although still probably cheaper than most other tours).