You've got a couple of options in my opinion, on the presumption that you can have the timber.
Extract it to a saw mill, best for the ultimate stock as they'd cut what you want and advise on what to do with the log. You'd need a forestry tractor and trailer of large flat bed with timber grab. You'd have to pay for that and then pay the mill so may not be viable unless you have links with a local forwarder.
Second and most busget option would be some one who mills with a Alaskan mill (If its a huge over sized log thats the only option really. Alaskan milling is really for cutting 'Through and through' though. If you wanted quarter sawn boards then a man with a woodmizer mobile band saw would be the best of all worlds. Though the log may be a bit big for the mill, may have to be trimmed to size, also may need a mini loader to pick it up on the feed table.
Thats a overview of whats involved, you could also buy a chainsaw and mill yourself. You'd want a MS660 or similar and saw alaskan mill with specific bar and chain. Mabye looking in the £1500 mark all in for the gear. Milling is hard work but is rewarding. The saw can obviously be used as a chain saw too.
Hope that helps, I've very keen on saving timber as 'waste' personally. I'd give a rate to do it myself but I'm a little way away down in Oxford! Theres lots of handy guys in South Wales who would be able to help you with this.
