How SMALL will it be? If it weighs under 20kg it will be classed as a model aircraft (in the UK) which might be of some help.
Airspace boundaries are shown in the Aeronautical Information Publication (AIP) for each state. I'm sure I've seen maps showing the airspace 'ownership' across a Region but I'm not sure where the came from - possibly the ICAO Regional Supplementary documents.
CAP 722 covers more than just airworthiness and I guess you'd have to follow everything if you wanted to operate the vehicle in UK airspace.
You might find it easier to do development work within the airspace of a State that has a lot (relatively speaking) of experience in the operation of UAVs - there are a couple that appear to be well known within the UAV industry.