jbailes...that sounds great, shame you are so far away or we'd come along for a listen!

To Guest... This is just my experience, but just in case it helps...
A couple of years ago, I bought a Casio Privia Stage piano...it is light enough for me to carry in one hand in a gig bag. It is an 88 note weighted-feel touch sensitive electric piano thingy which is a pretty reasonable substitute for a 'real' piano.

Its portability was the thing that I was looking for and it was much lighter and nowhere near as cumbersome as most of the other makes.
(They are about £500 new, so dearer than a keyboard but I think they are coming down in price.)

Normal keyboards, in my experience are just nowhere near as good to play, if you are used to a piano. My stage piano feels as though you are playing a piano not a keyboard. I love it!
It has its own speakers built in, unlike some. It also has a reasonable sustain pedal.

I take it to my local folk club and other places without too much difficulty and it is good not to have to rely on asking people to help you carry it as I can take it and set it up myself with no difficulty.
I use it to play in a piano vocals duo as well as the odd rock type gig and it seems to be at ease playing with its own speakers for small audiences right up to using as a keyboard or piano through full amplification systems. Very versatile.
It may not be an option for you to buy one right now but you could always try some out and keep watching ebay and similar as they are bound to get cheaper. Good luck! I think it is sad that the piano is becoming a less common instrument and I see the new portable electric ones as the next best alternative. (the more trad people still won't let me play it at acoustic nights though :-(   !!!)