The tubes are described as 'torn and extensively damaged'. Unless you're in a position to visually inspect it, then walk away. Yes you can patch it, but the integrity and strength of the material is now in question, and retubing would be the right way to go.
The Yammie engine looks like early 90s. No way of determining it's history, other than year of manufacture from the plate, but would be worth a few hundred. The trailer probably needs overhauled too including bearings, possibly new tyres.
Is that with or without VAT?