Thank you all so much for taking the time to answer and for your varied replies. It's good to know I'm not the only one with mice who love their greens MB.
Our terriers love digging out mouse nests and feasting on the jelly babies they find inside, but unfortunately in the garden they would cause more damage than they would save, so they are not allowed everywhere. I'm not sure what a whipsnake is CM but I'd rather not find out. I don't dislike snakes, just not in my garden

. There's no chance of enclosing our veg patch with a mouse proof barrier, although I would dearly love a walled garden.
pgkevet, I'm totally with you on the pain of crawling round planting and weeding veg which is why we try as many low maintenance growing methods as we can. Also why I now refuse to grow veg to sell, or even to give away - if others want them they can grow their own. I mainly grow sugar snap peas, as they don't have to be podded, but the mice were attacking those too latterly. This year, I am trying to improve our diet by eating more pulses, but if I have no success in repelling the mice this time I think I will just buy organic dried pulses which are not particularly expensive. Caterpillars and larvae are not too bad really - they are just made of the veg you are growing anyway - extra protein

. Humane traps might not be as humane as all that. It takes the poor wee mice days to get home, if they survive all the terrors on the way. Not as long as snails and slugs of course, but they all do come back. Or maybe it's just their chums filling the gap they leave behind.
Now that is ingenious Black Sheep

It wouldn't work though, as mice seem to have collapsible skulls so they can get through tiny holes, but that is the sort of idea I was hoping for. Keep thinking
TT - mmm, you could be right.
So, I've been doing some research, and thinking about your method Cans. I suspect it's the bitter onion taste and smell which deters the mice for you. I looked up some research and they find that mice and humans have almost identical taste receptors (including in mouse testicles

), and a 'new' receptor for 'calcium' - interesting. Mice seem not to like bitter tastes - onions - and strong smells such as peppermint. So there is a product specifically to repel mice made of peppermint oil with some other stuff in and...tada... it's not expensive. So I've sent off for some. But I thought I would add my own extras such as mustard, onion and chillies (it's worth trying - maybe Scottish mice are different to Norfolk ones TT, not such refined tastes). I'm hoping the oil will help the stuff to stick a bit but I will accept that I need to repeat the spray every evening (it rains here all the time) and it's only for a short while.
Please keep the ideas coming, but at least I have something to try now