So I've plumped for manual scanning my photos on an A4 flatbed, and making good progress, so now I need to think of a transport medium to send them to my friend. Looking at the play bank holiday sale (having already spent £80 with them today) they've 16gb SDHC cards going reasonably cheap, but before I add one to my shopping cart I just wanted to check... SDHC - the HC part is just "high capacity" right? It's still a SD card, and will work in SD card readers/devices yes?

No.
Well, sort of.
Not all SD readers recognise SDHC cards - be sure and check your reader is SDHC capable.
I can recommend the SanDisk multi reader jobs.

Wouldn't burning the photos to CD or DVD be a lot cheaper and easier? There's always the possibility of using a DVD player to view the pictures.

Seventh attempt... work you bloody forum!

This, or you can get a USB reader stick from Amazon delivered for about £2 (very handy for older PCs etc)

There's too many, I think even for a dual layer DVD - but it's a fall back option.

or even a usb flash drive - which might be the better option (to navigate the issues of SD/SDHC) all round. Hadn't crossed my mind!