I don't know what the current state of play is back there in Blighty - but I did find the experience of shopping for the pda quite frustrating.
None of the Comet/Currys/Dixons style stores seem to carry pda's anymore here in the USA. They can get you one on order - but you may as well get your own (which may save tax).
I hope you fare better than I did whilst trawling the shops.
Oh - ensure your new toy runs Windows Mobile version FIVE for TTNav6. Not the older version THREE. (Don't know where version 4 went).