Reasoned Response
Pandora,
If your house is where I suspect it is then there is a training field close by. That is a field that the landowner has allowed the JHC assets to use for landings. The useage of those fields is often curtailed for periods of the year when it may be predudicial to the use of the landowner, for example Pheasant breeding. This means that you may not see a movement for weeks and then suddenly it begins again. The field near you is quite unique and has certain characteristics that make it very useful for trainees on the conversion training. This would mean that a course of say 8 trainee pilots will all go there in a period of days and after that it would revert to its usual sporadic use. Please don't take that as any form of guarantee mind!
I apologise for the tone of some of the other replies, I personally as a Chinook Pilot thought you were just asking a simple question rather than seeking to grind any particular axe.