The weekend before is a no no, most folks like to get back before the day before the kids go back to school (4th September), the main shut down weeks are the last week in July and first 2 weeks in August so they are usually the busiest. The problem with September is the weather starts to get less predictable (less than usual any ways) and dodgy weather in Wales means drastically reduced visibility through the mountain passes. Thats my take on it any ways, I will go with the majority, but those are the things I was bearing in mind when I chose the dates, and I think any time during the 6 weeks holiday is going to be a case of dodging flat cappers and tin snails unless really lucky or go for a week day (which I for one cant do)