I can't speak to the enlarger on the left in your photo.
The enlarger on the right is a Philips PCS130. This is a condenser enlarger, and it requires MF condensers for proper coverage of an MF negative. Check the Yahoo Tri-One group for manuals, if you don't have one. (I could e-mail you the manuals, if you don't want to sign up to the group.) For 6x6 negatives, you need the F135 condenser on top and the F145 on bottom.
If you've already got an MF condenser set for the Philips, you'll probably need a 75mm or longer lens for proper MF coverage, too, but some wider lenses are more capable of covering an MF frame than others. £65 for an 80mm lens sounds excessive -- although prices do vary regionally, and I'm more familiar with prices in the USA. Of course, enlarger lenses are light enough that international shipping shouldn't break the bank, if UK asking prices are too far out of line....