Just want to give a few comments after my one week stay in Cornwall:
Cornwall has too many beautiful places to mention them all. We stayed one week and the weather was just nice, not too hot, not too cool, no rain at all. This made for an unforgetable stay. Here are a few of my personal highlights:
1) We stayed in the town of Fowey which turned out to be a gem. The town itself and its riverside is beautiful and it was much less overcrowded than I had expected. Nevertheless there are a number of restaurants and bars, so that we never got bored in the evenings. I was extremely satisfied with our location even though the apartment itself (Estuary Heights) was a disappointment. Btw: If you are staying there - someone on this forum told me that it would be a good idea to do the so called "Hall Walk" - and how right he was! You need to do this 3 hour walk that gives you a good overview of the river Fowey Estuary and the towns of Fowey and Polruan with stunning views as soon as the trees (most of the walk is situated in a forrest) disappear.
2) The Minack Theatre was the highlight I thought it would be. An outdoor theatre in stunning location. When we were there, the theatre group was rehearsing which made for an interesting experience. Not to be missed.
3) For cliff lovers: Both the Lizard Peninsula and Bedruthan Steps were amazing. Some of the most scenic landscapes I have ever seen. I went for a swim in Kynance Cove and liked it a lot! We also visited a very small town called Cadgwith on the Lizard Peninsula and found it quite charming.
4) The Eden Project was also not to be missed. I liked the way the park is structured a lot and the architecture of the biomeses alone is worth a visit. The tropical rainforest was very impressing - and the place also was less crowded than I had expected.
5) Knowing Dartmoor I decided to visit Bodmin Moor this time and have to admit that I found Dartmoor more impressing. Still, a walk in a moor is a must when you visit south-west England - at least when you don't know the atmosphere from home. I always find the atmosphere quite special.
6) St. Ives was very crowded - one of the few places where I thought that there were too many people. It is still worth a visit for the Tate Gallery, but I personally wouldn't think of staying there.
Overall, we had a great stay. Thank you to everybody on this forum who helped me to plan my itinerary. Your help was very much appreciated and you have been a great source of information!