A sparky hasn't been round 2 have. Then length is 20m run and both said they come of a spare in the existing cu but I asked if I can avoid that to save the drilling etc into my new wall and both said yes they will split into main of the tails. They have both quoted for 3core cable if this makes any difference and for me to run the cable and them to connect. I am on a budget so want to do as much as I can. But I'd rather be too secure than not enough. The box one has got me and I brought already is a metal clad 63a 30ma rcd Wylex with a 6a breaker for lights and a 16a for sockets so I can start the work in the garage hope this helps.
Murdoch - I am not asking to do this myself I rewired my hole old house 7 years ago and this was checked and fine so I am more than competent diyer. However am trying to save money as a new baby on the way so want to do this as cheap as possible but without cutting corners therefore asking for help( which I thought that is what this forum is for ) I am going to get all work signed of as it's a new build house etc. I don't understand why one said 2.5mm and one said 6mm the guy with a 2.5mm just wanted to come of a socket until I told him it wAs a spur...
Right, i'm going to be slightly brutal here - and i'm sorry in advance.
1) First of all...save all the crap about you having a child on the way - it's irrelevant, just flannel to try and get us to feel sorry for you. The Cheap as possible attitude without cutting corners is a fine line that's easily crossed.
2) Right, next point - i wouldn't trust any spark who signs off someone elses work unless he's been present and supervising you whilst you've undertaken the work.
3) Next, the fact that you say 'you are not asking to do this yourself' and that 'you rewired the whole old house 7years ago....and more than a competent diyer' don't add up at all, i interpret that (maybe wrongly) as you want the answers on here for you to do yourself and the whole scenario of other electricians turning up and quoting different things just adds to the storyline and is infact fantasy.
4) I understand this is the DIY thread, and we are supposed to be more lenient - but i think 100% honesty from the OP is required aswell. (here, i don't think thats the case)
My advice....(given the story)
Get a 3rd electrician in - you have 2 different quotes, so get a 3rd opinion and see if that sides with either 2 of the previous ones.
For what it's worth 6mm is overkill for what you're wanting - however, some electricians like to 'futureproof' and this could be a reason behind it. 3core cable or 2core cable is adequate, different electricians prefer different things. I would quote for 3core aswell, although im probably in the minority on this site with that one.
Another point, not sure why you need a 63A RCD? An RCD may not be needed at all, depending on how its going to be installed. Like others have said, it's impossible for us to advise on the size of cable, install methods ect... without actually seeing it for ourselves.
Post some pictures up, you may get a better response.