Firewood can keep you warm twice - the first time while you are wielding the axe! A log splitter can remove the effort and is a lot quicker - and likely to be safer. Tractor-mounted models are not that expensive.
As you don't mention the size of tractor you hope to use to power the splitter, I will give you a general round-up of some of the companies I suggest you contact for details. You should also note that for compact tractors you may need a PTO-driven hydraulic power pack.
A good starting point would be the Wessex log splitters, supplied by Broadwood International of Bordon in Hampshire. This range includes the Wessex Country LS100 for compact or large tractors with a category 1 three-point linkage. It's a hydraulically powered vertical ram and provides 10 tonnes of splitting pressure for logs up to 45cm in height. Price is £490 ex VAT. The Wessex range also includes a tractor-mounted professional splitter with an impressive force of 20 tonnes.
You should also have a look at the 7.5-tonne PTO log splitter from Arbor Eater Brushwood Chippers of Hassocks, West Sussex. This is a vertical machine and is suitable for domestic or professional applications. It features a swinging table so that logs just over 1m long can be split. Cutting speed is quoted as 4.2cm/s.
Another range you should check out is that supplied by Yorkshire-based Ryetec. As well as a wide range of electric and engine-driven machines, Ryetec offers 8-tonne and 10-tonne splitters in its Junior and Senior ranges. Every model has a 1m-diameter capacity but the Juniors are for logs up to 55cm in length, while the Seniors will tackle logs just over 1m in length.
Other contacts include Riko UK of Hampshire for the Italian-made Ballario and Forestello models, AT Osborne of Hampshire for the Zanon range of vertical and horizontal splitters, Ludlow-based Technorton for horizontal splitters and Fuelwood (Warwick), agent for Woodline.
Finally, remember logs can be heavy. You could consider a low-level vertical or horizontal splitter, so that the log can be rolled into position. Alternatively, and especially if you have a suitable timber source and are looking to supply logs on a commercial basis, consider a log loader to lift the logs from the ground to the vertical splitting position. The cost of heating fuels is driving sales of logs, so any equipment you buy now could pay for itself quite quickly.