Well i'm sticking to my guns on this one Kirkie
Tenerife is primarily a Winter Sun destination, Europe's most popular. High season is between November and April and the hotels are deffinately more expensive then. But I think the timing of school holidays in Britain affects whether it is busy or not more than anything - the February half term holiday period in Tenerife is just ridiculous and it coincides with the huge Carnival in the capital Santa Cruz.
End of the day I can see the sense in Bmi's seasonal nature of the Tenerife flights, there's much more profitable routes to use their aircraft on over the summer.
I was reading the local paper there yesterday and there was an article saying that the summer season there this year has started slower than in the past so lets hope it picks up, I don't like to see the place quiet too much!