It's a gut feeling based on the look, descriptions and pricing. I don't have any personal experience of the trader but would add that at the bottom of the market the trader's profit adds a big chunk the the price of the car as a proportion.
The level of consumer protection from a trader, despite the law on goods described/sale & supply etc is limited, nee bugger all on a 15 year old vehicle.
As long as you have an HPI and sense check of the Landy for signs of being nicked/cloned my feeling is at this end of the market to go for a private sale and be prepared to travel to find a good-un.
I'm over near Newbury/Swindon, and if there's any folk here (with more than a single post) wanting a hand to look over a truck - I'd be more than willing to have give a second opinion for the price of a cup of tea.
I don't wish to be negative for the sake of it, but I hate reading the avoidable tales of woe when people have bought a dog. These cars regularly cost thousands to put right and the owners feel committed to doing it. My advice would always be to spend what you haven't got, and then some more to get the very best car possible. Enjoy driving it and deal with the bank, don't spend your life under it and fixing it and waking up in the middle of the night worrying.
From one who has been there...