I do UA922 pretty often - the Fast Track lane often closes early. If you are not in F or C, PM me with a postal addresses, and I can send you an old Fast Track folder which you can use if it is open.

UA922 often gets in early - up to 30 minutes in my experience.

Last week the non-EU line was huge as Fast Track was closed - probably in excess of an hour.

Hoppa times as follows:

Sheraton Heathrow
Hoppa Bus H4

0521, 0533, 0545, 0603
then every 12-15 mins
until 2032, then 2100,
then every 20 mins until
2218, 2237, 2315

There are night buses (U3) - plus a walk - from the Central Bus Station:

23:17, Mon 23:29, Mon 00:12
23:20, Mon 23:35, Mon 00:15
23:37, Mon 23:49, Mon 00:12
23:57, Mon 00:09, Tue 00:12
00:17, Tue 00:29, Tue 00:12

check www.tfl.gov.uk and look for their travel planner.