Camping Europe by Train from London

[Tipperarely]

I'm sure this has been asked before but I just can't find what I'm looking for. I would love some advice on a good family eurocamp style campsite where we can stay in chalets or similar. Thinking smallish and peaceful (not too rowdy) but with pool and activities, nice scenery and cycling) to take my two kids aged 8 and 6 by train (e.g. Eurostar + TGV) in Europe next summer. Ideally somewhere we could get to easily by train from London plus local trains/taxi but be walking distance to town and maybe beach.
Any suggestions for France, Italy, Holland, Switzerland etc would be fantastic!

Camping Del Garda in Peschiera, Lake Garda. We have been there twice and never used a car. From Peschiera we have got trains to Venice, Verona and Milan. We flew and then used trains and boats to get around. We also hired bikes one day and rode for hours along the lake to neighbouring towns and villages.
We booked with Alfresco but if you book direct they have mobiles and bungalows. I hope that helps!