Hi,
Welcome.
Sounds like you have a lot of projects there and enthusiasm for the BBC Micro.
I think at one point someone was working on contiki for the BBC Micro, I think about 3 years ago ? But I've heard nothing since. I could be wrong though, perhaps it was some other desktop system but it does seem familiar.
Contiki would probably work very well on a BBC Master machine as they had a lot more built in memory as well, you got another 64K sideways RAM on top of the standard RAM available in the BBC Micro and you got 20K shadow screen ram too.
You might want to take a look (if you've not done already) at the sister site to this one which covers more general topics;
http://www.stairwaytohell.com