Garage conversion

[Fireinthegrate]

We have a double garage attached to out house. You can access it from the house through a door from the utility room.
We would like to convert half of the garage into a room. We actually want it to be a dog room, somewhere I can have a shallow tray with a shower tap to wash them, and then they can dry off in there before coming into the house.
Anyway, approx how much will a conversion cost?
Do I need planning permission or building regs permission?

I would say 15-20 k depending on spec and size, but plumbing, windows and external doors will probably mean it is closer to 20. I have to ask (as a non dog owner so excuse my ignorance!) why you can't clean and dry the dog in the garage?! It would be a lot cheaper!!

The garage is full of 'stuff' so could really leave a wet dog in there to dry out, its cold too so probably would catch a chill.
At the moment I cold hose outside, give a good rub with a towel and let them (2 dogs) into the kitchen and they can't access the rest of the house til they're dry.
But OH wants to get another dog, and I have said I don't want 3 wet dogs messing up the house so I want some kind of 'dog drying area'. It's his idea to do a garage conversion for them, i was thinking of partitioung off a bit of the garage, putting a bit of carpet down and some dog beds and maybe a heat lamp. His idea is £'s more!