my lawn has bare patches caused by the wetting on it

You need to remove at least 3-4 inches of the soil where the dog has wetted. Replace it with some nice new soil and it should regrow quickly. Grass doesn't usually germinate or grow much below about 6c so in cold weather you'll need to be patient.

I reseed some wtted patches on a customers lawn last autumn and the grass took about 10 days to gerninate.

It might be worth covering the reseeded areas with some net or mesh to keep the birds from eating the seed before it gernimated.

i would definatly keep the dogs in a dog run if you want a nice lawn realy .

I've just seen an article in a gardening magazine which suggests covering newly sown grass seed with polythene until it germinates. Never tried that myself though.

Well the same thing will happen every time the dog goes out (especially if a bitch). You can buy something called 'dogrocks' to put in the water bowl, which apparently stops the burning of the grass when they wee. I havent tried it and don't intend to. If you see where your dog wees and immediately pour water over it that helps - but can you be bothered? I certainly couldn't.