Can we afford to buy a home?

I had an email this week from Rebecca who wrote:
I'm about to turn 30 and I live in a rented smallholding in the UK. My husband and I live as simply as possible, rearing nearly all of our own food and spending as little as possible. We are very happpy and love our lives. We're both well educated and work in environmental jobs, which we both enjoy, feeling that they are worthwhile and really