Hi Taffy
We stayed last year at Amerden Caravan Park. It is very near the M4 and between the Thames and Jubilee River. It is a lovely site with hedge divisions, H/Up, and the toilets/showers are very good. We have bikes and it was very easy to cycle into Windsor along the river paths - about 5 miles on the flat. We locked up the bikes near the bridge and it was easy to walk around the town. On another day, we went on a boat cruise along the Thames. Dorney Court worth a visit and can cycle to it. The only downside is the traffic noise from the M4. Try to park nearest the entrance. On the second night we pulled down the roof and this helped a great deal. Third night we tried vino and that worked a treat !!
Hope this helps, Chris