Here you are, from CAP 413. The highlighting is mine.
Flights Crossing Airways
An aircraft requiring to cross an airway should make its request to the appropriate
ATSU.
Wrayton Control, G-ABCD, request
crossing of A1 at Wicken
G-ABCD, Wrayton Control, pass your
message
G-ABCD, T67 from Borton, 20 miles
north of Wicken heading 220 FL80
IMC request crossing clearance of
airway A1 at Wicken FL80 at 1033
G-ABCD, cleared to cross A1 at
Wicken, maintain FL80 whilst in
controlled airspace. Report entering
the airway
Cleared to cross A1 at Wicken
maintain FL80 in controlled airspace.