Shouldn't be hard to find - a twin with life-expired engines shouldn't cost you too much either, although a life-ex piston prop would be cheaper and easier to obtain. Life expired old military engines are easily bought for under £10k which you could then put on a stand.
My favourite website for aeroplane window shopping is here:
Planes and Aircraft For Sale - Light Aircraft, Autogyros, Helicopters ... (UK) although for a twin, which are more rare, you might want to ask around some maintenance companies and see if anybody knows of anything.
You might also look at MoD disposals - you might be able to get a life expired military aircraft quite cheaply. Nothing there at the moment, but worth keeping an eye on.
http://www.mod-sales.com/direct/vehi...elicopters.htm
And, believe it or not, eBay. It's amazing what comes up there!...
http://www.ebay.co.uk/itm/LYNX-HELIC...item25a263e28f
http://www.ebay.co.uk/itm/GULFSTREAM...item35e73fce1d
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