I just downloaded the brochure for the plug in version of the Toyota Prius (from the Toyota website). Found a bit about charging which I have quoted below. It is worth looking through the whole brochure though:

"CHARGING AT HOME Charge in only 3 hours using a domestic plug socket. Just like your mobile phone. Alternatively, install a dedicated wall box at home or use a public charge point to fully power up in approximately 2 hours. The dashboard LED display will keep you up to date on your charge status."

So you can charge it from a standard wall socket. As long as you have the correct cable.

Presume other plug in hybrids will be the same, but you'll need to check

As stated above, the majority of plug-in hybrids have (relatively) small batteries. This means that you can charge them quite happily from a domestic 13A socket.

My own 225xe plug-in charges from 3% to 100% in 3h15m from a conventional 13A socket, and BMW's literature says it takes 2h15m from a high-output wallbox. My 10p worth is, an hour saving doesn't justify having a wallbox fitted.

The owner's manual will be full of warnings about not using extension leads to connect the car to a 13A socket: this is a bit misleading because you can buy heavy-duty extension cables that can carry 13A continuous current from the likes of B&Q etc. I've used an extension regularly without problems, and neither the plugs nor cable get hot.

Most plug-ins adapt their current draw based on the type of socket you're plugging into. The BMW draws a max 10A when configured for the factory-supplied 13A charge cable.

I would have thought that it made sense to run this kind of steady demand for a number of hours from a dedicated circuit-breaker on the distributor box, as you would for a cooker or a shower. Adding it to a ring-main would quite likely cause trip-outs when some other demand came in.