Andy, in another life I used to sell them and run training courses on them.When they first came out they were innovative as they were the only unit out there that did not require a primary connection on DIS systems and had the ability to test against known parameters by you selecting the vehicle you were testing.
Since no data has been written for years, this feature really has become redundant although I have written a few spec files myself (still have a 400).
The scope pattern is just O/K (uses an 8 bit analogue to digital convertor) so the patterns are not as "crisp" as later scopes.
The multi scope function is great (still use it) as you just about graph anything you want without buying extra kit as its all there; 2 special scope pickups, low and high amps pickups, vacuum pick-up etc. etc.. These patterns can be synced to a number of inputs.
Battery test facility is top notch as is the charging and starting tests. The cranking compression test looks great BUT be careful on V12 engines as it may report the wrong cylinder (usually reports the one after the faulty one) but this is corrected when you ask it to "diagnose").
Gas analyser is an Androis (sp?) bench which is very common these days, but is very sensitive to blocked filters and water so we always fitted a diesel engine water trap to ours. Also keep an eye on the O2 sensor - change every two years.
They were approx $32,000 new back in the early 1990's.
I would think 3000 pounds is a bit rich. Going on second hand units over here and doing a quick currency conversion, more like 1200 to 1800 pounds.
HTH
Cheers
Peter Wright