I don't live in the UK, so I can't really offer much useful advice about buying a Plextor.
However, I can offer advice about getting an IDE adapter.
First off, I've had a lot more success getting SATA to IDE adapters running than USB to IDE adapters.
I'm currently using this Syba brand SATA to IDE adatper: https://www.amazon.com/gp/product/B002O … &psc=1
However, I can't seem to find that exact product on amazon.co.uk, but this device looks suspiciously similar: https://www.amazon.co.uk/StarTech-Bi-Di … de+adapter
Of course, you'll want to make sure that your power supply has Molex/4-pin power outlets. Otherwise, you'll need to buy a SATA power to Molex adapter in order to power the drive and the adapter.
Also, I'd like to warn you and anyone else who may be reading to NEVER buy this product: https://www.amazon.com/gp/product/B00BI … &psc=1
I can't go into detail right now, but all you need to know is that it failed on me.
Also, Kludge is a UK based dumper who apparently owns multiple Plextors. You might be able to convince him to part with one of them for cheap-ish if you ask nicely.