Where to start.
There are so many places; I think you will need to be more specific.
The all time favourite is Le Touquet (L2K). Hundreds of Brits fly their each year - it is always a good day out and the French are use to us so every one muddles by. There are a few matters to consider but there are also loads of past threads on trips to L2K.
Every where in France, the low countries, Germany and Eire is fine. You will hesitate at first to go further afield, and there are a few gotchas, but with a little planning and a few questions on PPRuNe all are within your grasp.
You should therefore decide what country you want to go to and what places you would like to visit - then ask the forum.
As to the inevitable sea crossing that has also been done to death. To summarise:
1. The sea is bl**D* cold all year, and the visibility over the sea can often be much worse than over the land,
2. You need to think about how risk averse you are. If you are not risk averse at all just pray the engine doesnt quit and all will be well, if you are risk adverse think about your survival strategy should the worse happen.
3. So far as viz goes maybe go with another pilot the first time just to see what it can be like over the sea when there is no obvious horizom.
It is all there waiting to be explored but you need to be a little more specific beyond the points I have covered.