Patrick
What type of stickers were you thinking of for the doors?
We have now ordered the standard National identifier stickers:
These are 40mm x 250mm and will be available in both external vinyl and internal "cling" types.
Should be with us in the next week or so.
Locally we have sourced some Hertfordshire logos, like the ones I use on magnetic backing on my doors (I bought a roll of magnetic film of eBay quite cheaply):