Just stumbled on this thread - that looked like a nice and useful device Alf - thanks for highlighting it: it's certainly affordable
I guess the problem that many of us diesel owners have is that MG Rover only more recently made their cars OBD compliant - usually at the last minute to comply with homologation requirements! 2001 for Petrol variants and 2004(?) for Diesels.
Therefore to get useful diagnostic information, one is a bit more stuck for suitable tools. I got a T300 for my MGFs, but unfortunately it doesn't read diesel. T4 is of course the best bet - particularly if you are taking your car to a specialist, and especially of you are looking at activating particular functions. But a T4 is out of reach for most of us home DIY'ers to buy for home use - and probably also requires some training to use it safely.
I've now got a pscan.eu diagnostic unit off Philip - and this really does work really nicely on all my MG-Rover cars (MEMS1.9, MEMS2J, MEMS3 and the Siemens ECU on my ZTT 2.0 CDTi). The latter was having a number of problems with running, occasionally stalling while running (not at junctions - weird) - but revealed that the MAF was providing no signal whatsoever. I removed the RoverRon box, replaced the MAF, and normal service was restored all thanks to that pscan.eu device. And to restore performance, I went round to visit Kenton who did a thorough job of servicing it and providing a sneaky 160 remap via T4
Diagnostic devices should be available for everyone's tool box IMO - and fits well with professional tools such as T4 IMO