I paxed on the EDI~LTN route extensively in 2000/early 2001 on a project and often chatted to the FC and was even on the flight deck for one trip!
I learnt that it was, mostly, up to cruise in 18 mins / in cruise for 20 and down. making a wheels-to-wheels of 50/60 mins depending on weather and the approach available. Sometimes they DID go higher and gain the benefits of the thinner air, they said. Also, the route was pretty standard - except for the days when it wasn't! The weather and other other a/c movements can change things.