Letsby, I haven't taught at Wallop since 2001 but I didn't change my nom de prune when I left as I'd got quite attached to it.
The Lynx and Gazelle Flying Instructors Handbooks and Student study guides all refer to hover Tq plus 10% for a normal into wind transition so I'm sure you were teaching the correct technique.
SASless - I don't know what one would use on, say a Puma for example, when there is no tqmeter just a pitch indicator - there must be a Puma QHI who could tell you. If you do have a Tq meter in % then you could equate your N1 or TOT limit to a Tq figure and work backwards from there.
We all know that you can get into forward flight with not much more than hover power but the 10% figure has at least 5 uses:
1. It highlights that to make a standard transition into wind ie one in which you can climb and accelerate you will need a certain amount of power in hand above your hover Tq. (this is for Brit Mil types of transition not CAT A or any clever stuff like that).
2. As WDE says, it stops students trying to overtorque during a transition because they have a specific Tq setting to aim for.
3. It reminds you to use a different transition technique eg cushion creep if you don't have enough power in hand.
4. It is a good ballpark figure for vertical climbs out of confined areas where a towering take off is required.
5. It is also a good ballpark figure for downwind transitions.