In reply to gordo:
I've been doing this for ages, most of my mates do exactly the same.
Unless you have weak ankles or are carrying an enormous, heavy rucksack (and even then, sometimes) I find trail shoes lighter, comfier and cooler than boots. The only time I wear boots now is when I'm also carrying or using crampons.
Go for trail running shoes over 'approach shoes', approach shoes are just a beefed up pair of trainers (so heavier, less comfortable and with worse grip) and seem to be designed for American approaches or scrambling rather than British approaches (rough tracks and bog).
Final tip, keep another pair of shoes in the car for the drive home for if your trail shoes get wet.