Here we go...
The UK does use 3 minutes if you have R/T failure whilst on a heading. Here is the reference
UK AIP ENR 1.1.3
3.2.4.1
(c) (i) If being radar vectored... continue in accordance with ATC instructions last acknowledged for 3 minutes only and then proceed in the most direct manner possible to rejoin the current flight planned route.
I hope this is useful. I am pretty sure that in reality it would take longer than 3 minutes to find the right book on the flight deck. I suppose the best thing to do is adopt standard aviation philosophy and if you come across something you've not seen before - either eat it or start your stop watch!
G W-H