That's quite a good size some of the allotments on my site are smaller than that, mine is 334 square yards....but your're probably not including your shed as part of your vege patch are you?
I'd be happier having a vege garden that size at home rather than an big allotment. At home any free half an hour can be used, there are no vandalism or theft problems. I wouldn't have to worry about weirdo's creeping up behind me when I'm working as we don't have any security fencing and sometimes I'm there on my own.