How about something like this?

http://www.screwfix.com/app/sfd/cat/...05479&id=19394

We have one and i use it anywhere I'm not happy using the chainsaw - like
above shoulder height or up a ladder. It says max 115mm in wood but I've cut
trees much larger than that. I'm sure it would manage a sleeper all be it
fairly slowly. It's particularly effective at pruning.

Sam