I feel I know a little about buying a used
Elektra, mind you mine was a T1.. With a bit of work, you would have a beautiful system.
Here are some of the things you might want to think about.
Measure where you plan on placing it in your kitchen. It's bigger than it looks.

Don't forget to measure how high the system is and how much room you have.
Did they store it indoors? It's important that the boiler and tubes full of water did not freeze.
Did it have a water softener? If not, (or even if it did) you may have to descale it. A chore, but not too difficult. Fairly easy if you are willing to take thing apart and back together.
Age? The face plate will likely have the year of the build. You are likely going to replace the head gaskets in each group head. Perhaps there are other gaskets that need replacing as they age? I replace everything on mine since I had it in pieces and don't expect to ever have to do it again.
The pump may need some prompting to turn as it has sat for a while. Mine worked just fine.
Running from a bottle is not recommended for any length of time as the rotary pumps like positive pressure. A flojet accumulator can be used to over come this and pressurize the water from the bottle for you.
Not being in the UK, I can't say if it's plug compatible with your wall outlet, but others have (or will) comment on that aspect.
Missing parts? All can easily be replace, but it will of course cost you some money.
The drip tray is made up of two pieces: a splash guard and tray with a hole in the bottom. The cup warming tray looks to be in place. The stupid little key to program the system if you want to change the amount of flow when you press a button? Double/single baskets? Springs in each portafilter to hold the basket in place?
Look in the interior for any "extra" wiring that doesn't look stock. Mine was missing the emergency heater cut off, a $20 part (or so) that was simple to replace. I didn't notice it missing, but a sharp eyed fellow Elektra owner pointed it out.
If you do elect to plug it in, make sure there is water in it (slosh it around?), don't ruin the pump by running it while dry.
=-=-
Mark
edit: fixed url to my restore