Thanks for the advice - it tallied with my own beliefs, I just wanted to make sure... (sometimes it feels like there is toooo much info out there!).
As it happens, whilst looking at another thread (in the LCD TV section), it mentioned using promotional codes and 'instant cashback' via egg credit cards. Now, I have one of those, so looked at their website, and for a limited time only (five days ending 17 April - tomorrow) egg were giving 10% instant cashback on all purchases from Dixons.co.uk., instead of the usual 5%
Dixons happened to be (joint-)cheapest store on Pricerunner: £608 (incl. VAT , plus about £4 for standard delivery); plus the thread mentioned a promotional code that gave another tenner off
So, I've just ordered a legit Sony HC5E, from a big brand UK outlet (although it is part of DSG!) for what my credit card statement will hopefully say is around £540... Not quite as cheap as some on eBay - but still very good, and without all of the hassle that Mark mentions in his reply.
AVForums strike again!