How do I connect this to the mains

[#1]

http://www.amazon.co.uk/Worx-WA4977-Sonicrafter-Universal-Carbide/dp/B00CEU5N8I ?  (I haven't tried anything like this as I've not had the need, my entire tool (DIY store own brand) didn't cost all that much more than this blade!).
A normal 'general purpose' (much cheaper!) blade is OK for plasterboard and normal plaster.

[#2]

Having seen the rate my carbide discs used to wear and the small amount of carbide depth I doubt that it is cost effective
I will stick to my diamond cutting discs

[#3]

Sounds like you have military-grade plaster in your house, tough enough to resist bullets and shrapnel, are you living in a bomb shelter perchance?

[#4]

Nope but the house was built by a man (on his behalf) who had a fabrication and galvanising company
That is why I have a metal shed and a load of galvanised rectangular rolled sections lying about - very useful they are too

[#5]

I wonder if he mixed metal shavings into the plaster, that makes for some pretty tough stuff, as used in bank safes and the like to kill the cutting blades of anyone trying to break into one...