Thanks for all the replies gents. The point about steep learning curves was very enlightening, as although i've used high-end stuff before (it wasn't mine) i wasn't thinking about the lack of time to get up to speed on the equipment. Costing was a lesser consideration as the lens desired was a telephoto and understandably they are by nature expensive. The suggestion of the 550D Canon was good, it seems to have many fans in the prosumer market, but i'm generally averse to buying equipment that i won't be using all the time.
One's present steed is a small Leica, it makes excellent images, but sadly the zoom/telephoto capability is by it's nature very restricted. Thanks for the recommendations of hire companies, that's 2 that i didn't know of before
SHJ