In reply to alooker: Just done my own last week. McNett Seam Grip and Tenacious Tape. They do a repair patch kit also. I bought the tape and teh seam grip seperately as I had a well punctured thermarest to repair as well.
In reply to alooker: you can buy goretex patches in a (limited) range of colours for around £8 and do it yourself, otherwise it will cost £20+ to get it done professionally and won't necessarily look any neater.