Rewiring Loft Conversion

Hi all,
Could somebody please give me a bit of help regarding rewiring a loft conversion?.
We live in a small 2 bedroom bungalow which had a complete rewire 5 years ago. As all of the floors are solid, all of the wires from the RCD CU run up to the loft first.
In the loft conversion is a bedroom with en suite and a small study.
The CU was put in the most awkward position in the Kitchen and is very difficult to get at(for connecting new circuits) without dismantling kitchen units.
When rewiring the loft, I was going to extend the existing ring main and light circuit, but obviously this would mean not being able to seperate upstairs from downstairs.
There is a large cable (I think 6mm T+E), which runs from the CU, into the loft and out the other end to a detached garage. The garage then has it\\\'s own RCD, which is split for lights and sockets.
I know that outbuildings are meant to be kept seperate, but can somebody tell me if I can connect another RCD to this cable in the loft to run the loft sockets and lights and therefore keep them seperate from downstairs. Somebody suggested that I should disconnect the garage and connect a RCD with at least 3 MCD\\\'s to supply the garage and loft? - it doesn\\\'t sound right!!.
The CU is split as follows:-
RCD
Kitchen Sockets - B32
Other Sockets - B32
Garage - B40 which goes to a seperate RCD split with B20 and B6
Cooker - B32

Non-RCD
Burglar Alarm - B6
Lights (Left hand side of bungalow) - B6
Lights (Right hand side of bungalow) - B6
Boiler - B6

If I do extend the existing ring main, I wouldn\\\'t exceed the 100 square metres maximum.

Any advice or ideas would be much appreciated.

Split the existing ringmain and lighting circuit to incorporate you proposed wiring and then identify them on your fuse board.

Just wondering, are you the LaughingGravy I know from elsewhere?, from the computer forum from a well known computer magazine?

Thanks il78 - I thought that would be the case. I was hoping that there might be a way to split the upstairs and downstairs?.

Adam - I'm sorry but I am a different Laughing Gravy - there must be a lot of us about).

Anything is possible, but it depends on how much effort who want to put in......

I don't mind putting in the effort, but does it involve removing kitchen units and tiles?.
I think that I might be able to feed cables down the wall with other CU cables(although it is very tight!), but the CU is right at the back of a corner unit and the only way to run new circuits from it, would be to remove the kitchen cupboard for access - I suppose that might be the only way?.
Any other suggestions?.