At £1,020 each you wouldn't want to link too many together, just buy a big one for less money in the first place. Or are you thinking of joining a few of the 650w £59 specials from Netto ?
Nah, no clever electrickery required; we do this all the time on ships, albeit with 3 phase gennys. Provided you sync the phase, a functional modern(i.e. less than 30 years old with AVR etc) genny can be joined to another without tears or all the smoke escaping. I'm not aware of anybody syncing single phase gennys, but it is technically possible.
They keep themselves in sync; it's a self regulating process. Simply put, when one genny tries to spin faster, it takes a greater portion of the load and slows down. The only tricky part is getting the sync in the first place, A quick google turned this up for syncing single phase and this for 3 phase. The 3 phase one leaves something to be desired, but covers most of the important bits.