Thanks all.
The mother earth news website is fab -- I live in Scotland in an area with acidic soil (according to my soil tester kit!) so I figure potatoes will do well and the website has some useful information on growing potatoes and about last frost dates.
The membrane sound like a good idea as we are planning to plant strawberries. The last few summers have been very wet here so I'm actually more worried about too much rain especially if we do potatoes.
Fortunately, or unfortunately, the neighbours garden is in a worse state than ours! I have started a few plants indoors as the growing season is quite short.