Lidl's (a discount supermarket) recently had in a batch of electric chainsaws, £45 each plus £10 for a spare chain. I went halves with a friend, and we spent a merry couple of hours chopping up various bits of knotty log and tree trunk that were either too large or tough to saw by hand.
The chainsaw (2200W I think) made light work of anything we attacked. The only thing we ran out of was oil; the saw came with a 200mL bottle, which filled its 135mL tank okay, but this supply was quickly drained. The manual says to use Parkside Bio Oil. A Google search for this gave no relevant results, but chainsaw bio oil got us these: