I got everything from ebay. You could technically get the bits from Halfrauds except for the PAC-ROEM, I've only ever seen that in the US.
PAC-ROEM:
http://cgi.ebay.com/ebaymotors/PAC-ROEM ... enameZWD2V
Fascia adapter (Autoleads FP2203):
http://cgi.ebay.co.uk/Fascia-plate-Faci ... dZViewItem
Looking at the fascia adapter, I'm not sure it does convert to a double din size slot. Best wait and see if someone with a double din HU can comment on how they fit and if you need it or not. Sorry for the doubt, I dont have the instructions for mine any more and I was quite sure that you did need it, but now I am unsure.
On the case of the aerial adapter, does the HU you want to fit have a hole in the back about an inch deep or a stub/stud? These are two types of aerial I know of, the BOSE being the long hole kind. The second is a stubby "button" type. Sorry for the flakey descriptions! If your HU has a hole then it will work out of the box, if it has a stub then you need a converter.