Although your kitchen may have been professionally fitted insofar as the base units, cupboards etc, judging from what you have said, I don't think the electrical side of the project has been carried-out at all professionally. The fact that whoever carried-out this electrical installation has completely misjudged the number of socket-outlets that are required, and has to resort to running extension leads, tells me that it certainly wasn't a professional electrician who carried-out the work. Big red flag here!
A professional electrician would have designed the installation in such a way that there would be a sufficient amount of socket-outlets provided throughout. In all probability, the kitchen fitters you hired will have done the electrical work themselves so to avoid paying for the services of a professional electrician. They've probably charged you a professional electrician's rate though and pocketed the difference, as kitchen fitters often do.
I for one certainly wouldn't even begin to contemplate supplying a washer/dryer via an extension lead. Have you checked the manufacturer's guidance? Some manufacturer's advise that their appliances NOT be connected to extension leads.
Electricians are required to work within the scope of the 17th edition wiring regulations (BS 7671). We have to take into consideration whatever guidance a manufacturer may issue vis a vis the installation of their products. If we comply with such guidance, then we are deemed to be complying with BS 7671. But if we ignore the manufacturer's guidance, then we are considered to be in non-compliance with BS 7671.
The thoughts of other electricians on this matter can be perused via the two links below:
http://www.electriciansforums.co.uk/threads/melted-plugs-and-sockets.3205/
http://www.theiet.org/forums/forum/messageview.cfm?catid=205&threadid=7332
Naturally, the kitchen fitters have told you that their work is "totally safe" and that you have absolutely nothing to worry about, in which case whoever did the electrical work in your kitchen will have stated so by way of the Minor Electrical Installation Works Certificate(s) or Electrical Installation Certificate(s) that they put their name to. They did give you certificates? Right?
Regarding the extension plug being right next to the gas meter ..... I think you better read this:
http://www.electriciansforums.co.uk/threads/socket-near-gas-pipe.18630/
The only sure way to guarantee safe, quality, professional electrical work is to use a competent, professional electrician who know what he is doing. I know plenty of kitchen fitters who carry-out electrical work, but don't know of a single electrician who installs fitted kitchens. Go figure! Has your local authority building control signed-off on the electrical work yet?
In summary, I don't think that you are overreacting. On the contrary, you have quite genuine concerns here. You could seek the advice of a professional electrician and obtain a second opinion. Alternatively, if you are resident in England or Wales you could refer the matter to whichever Part P scheme the kitchen fitters belong to, assuming they are actually registered under the scheme. If not, they are in BIG trouble:
http://www.electricalsafetyfirst.org.uk/find-an-electrician/part-p/
