ST,
SNS3Guppy, The reason I asked was because under UK aviation law, you need a written permission to go above 250 kts in Class G airspace. I don't think ATC can give ad hoc permission on the day; Class G doesn't "belong" to ATC.
Correct.
UK MATS Pt 1...
In Class E, F and G airspace, conflicting traffic may not be known to ATC and so it is necessary for all flights to make use of the 'see and avoid' principle. In order for this to operate effectively, controllers shall not authorise a relaxation of the airspace speed limit.