Hi folks,
ok - I have now had a clear view of the bird in question and can shed a lot more light on its identification.
Firstly - and sorry
it is most certainly not a nightjar!
It is a lot larger - almost pigeon sized - but not as stocky. It is predominantly brown in colour and has a very long and fine beak - which seems to curve down slightly. The call seems only to be made during flight and carries a very long way. It seems to circle around a territory of apx 500m in diameter, calling as it flys. Flight is made up of what I would now call fairly "normal" flapping followed by a period of gliding. I am now more intreaged than ever to identify this bird. I have looked in books and on web - The closest resemblance seems to be a curlew - but the call is definitly not the standard curlew call, (dont know if there is a few different types of curlew call). The second one that caulght my eye as a possible candidate is the whimbrel, - not sure how feasable that is? but the call that is on the RSPB site is the closest that I have heard so far - but still not exact.
Thanks for your continued interest and help...