I am thinking of getting one of these machines.
As far as I can see the only difference between them is in the HDD size
Yes?
The price difference though, is about £160
You could buy 2 500GB drives for this.
I assume like my other Pana HDD/DVDs you can't upgrade the HDDs
Am I right?

You are correct on both points.

Thanks for that confirmation

I did buy myself a BW780EB with the intention of copying stuff across to BluRay, but the cost of these discs are obscene!
A 50GB Panasonic BD RE costs £25.95 or a 3 pack for £79.99 (Amazon)
And I thought paying £32 for 4 DVD RWs a few years ago bad enough.
Unfortunately the price of BluRays seem to be increasing on ebay (Japan) rather than the other way round

Certainly the bluray disc marketplace is difficult to understand.

Disc speed tends to be a measure of how recent discs were produced.

The best price I have found so far for discs which are bizarrely faster and significantly cheaper than other slower discs even from the same dealer...were some I bought last week from 'Annova'

Panasonic 25Gb 6X speed BD-R's @ £16.33 for a spindle of 10