Bignev, there is a school of thought that advocates putting RCD on everything from the toaster to the kitchen sink.
There is nothing wrong with RCD protection, if used wisely though.
RCD main switches are good in certain installations, but not in the home, the RCD pops, you have no lights, you break your neck falling down stairs to reset the RCD..you didn't die of electric shock though!!
RCD protection has been advocated for sockets on the ground floor of installations because people have a habit of using electric equipment out doors and then damaging the cable or the tool, and getting serious shock or worse as a result. The problem with this is that electronic equipment uses switched mode power supplies, of a type most commonly found in computer equipment. These types of PSU's create what are call harmonic currents, and they appear on the neutral conductor or the earth, in domestic situations they are 99% found on the earth cable.
The problem is that these harmonics are the very type of current that RCDs detect, consequently if they build up enough then the RCD operates. Each piece of equipment will typicaly create about 5mA of harmonic current when in use. In your home the type of equipemtn that does this are, Hi-Fi seperates/systems, TV's, satellite/cable TV boxes, video's, DVD's, computers and related equipment, plug in phone chargers etc.
Many years ago this was not a real issue, but in the last 5 years or so the growth in the the of the switched mode PSU in just about everything has sky-rocketed. This is creating real problems in some households.
I don't have enough hours available tonight to list all the call-outs we have attended in the last 6 months caused simply by harmonic currents causing RCD's to operate. This costs the home-owner money.
Many will try to say there is a regulation to cover this, there is not, and the NICEIC do not advocate putting all sockets on RCD protection.
Kitchens present a special danger, we all switch things on and off, plug things in and out with wet or at least damp hands, we shouldn't, but we do. This creates significant risk of shock, and as such the installation of an RCBO protected ring main is critical in the kitchen. If you budget can stretch to it, the obvious compromise would be two circuits in the kitchen, an RCBO circuit for sockets on the worktops, and a MCB type B protected circuit for the outlets feeding the fridge, freezer and similar white goods, although washing machines do present a significant risk, they are likely to trip dc sensing devices.
If you have a socket that is likely to be used to feed a lawnmower or used outside, then there are a couple of things you can do. Firstly you could install a circuit, MCB controlled, that feeds a waterproof socket mounted on the outside of the house, this will incorporate an RCD for protection locally. Secondly, you could install an internal RCD protected socket closest to your rear door, where your likely to run cables from into the garden, or thirdly, you can simply protect the circuit in the kitchen that this socket will be on with an RCBO.
The use of RCD/RCBO protection upstairs is not required, however I would add one word of caution. If you intend to put sockets in your loft void, I would use RCD protected sockets should you spur them from the upstairs ring, unless you are 100% confident that no moisture can enter the void.
The decision about what you do in your home is your decision, of course there is always the cost to consider, make no mistake, RCBO's come in at about £40 each, as opposed to £7 for a Type B MCB. You know what equipment you have in your home, we do not, and you know how it is used. You need to consider all these points carefully, then look at what you can afford to pay to achieve your aims of a new installation, but be assured that it will operate effectively and how you want it to.
