Sounds pretty standard.

If you cannot afford (as most can't) RCBO's for al circuit, just use a new 17th edition DUAL split load consumer unit.

You can also get some of these which have a few unprotected ways which are good for the submain to the garage for example, aslong as the cable is routed correctly to negate the need for RCD protection.

DO NOT use a single 30mA RCD to cover the entire install - this is not compliant.

If you do have TT, I strongly recommend having it converted to TN-C-S.  Depending on your DNO, this could cost as little as £18.

A dual split load board is used to satisfy the regulations in terms of convenience and safety.

Safety - not in the sence of protection, but in the sence that if there is a fault you only loose half of your power (lights).  You should have wired your property with a couple lighting circuits and a couple socket circuits (ideally a couple per floor).  You then place the socket circuit serving one area on one RCD and the lighting circuit serving that same area on the other RCD.  This way, if an RCD fails you still have power available to most parts of an installation.

If the cable to the shed/garage is SWA or routed so as not to require RCD protection (no burried in a wall less than 2" etc) then you do not need to RCD protect it at the origin, you can supply it from a non RCD protected way (some dual split loads have a few non RCD ways).  You could then use a consumer unit with RCD incomer in the shed/garage.  No need for a dual split out there.

You do not need to supplement the earth to your shed unless there is main equipotential bonding that needs to be done out there?

Thanks again. The new wire first fix is not yet complete . I'm open to sujestions , with the dual boards we've talked about, am i right in saying both sides can be protected with individual RCD'S.
Last board I've done years ago half on RCD half not (with mcb's)
Would you protect all circuits via an RCD?

All circuits need MCBs or fuses as they always do.  The RCD does a different supplementary job.

17th edition DUAL Split Load (with a couple non RCD protected ways.


16th edition 'traditional' Split Load


Not my choice of brand, but it's what google found  

This is brill .Thanks for pics. Not your choice of board though. what would brand name be of your choice? or do you mean RCBO'S board? is prefrence to you.

What do you think is the biggest significant change in the 17th edition?

you may find this good reading

http://www.esc.org.uk/forum/index.html

Quote:


There is the issue of a loss of supply neutral which could make your earth, any exposed and extraneous conductive parts connected to it, become 230v. If you have extraneous conductive parts in the garage, then you would need to export the equipotential zone from within the house, to it, using 10mm earth. There are mixed opinions on this, and the prefered option if you do have PME is not to export it at all and TT the garage, earthing the armour in the house CU, but not in the garage. If you have extraneous conductive parts in the garage, i.e water, then bond these to the MET of the small consumer unit, where the TT's earth is also connected. A single 30mA rcd main switch will be ok in this instance, because its a couple circuits in a garage, it wont affect the house install in anyway.

If the wiring to the cooker switch and cooker isnt buried, i.e, surface trunking, then no it doesnt need an RCD protecting it. If the cable is buried less than 50mm in the wall, then it does. If this is an existing install of which your doing a PIR, then a code 4 would be applied to the buried cable scenario I just mentioned.