This should be a nice easy cache as you can drive to within a couple of hundred feet of it.
The church is signposted on the Buckingham to Whittlebury road. It can trace its history back nearly a thousand years although most of the 'modern' parts are only about 700 years old! The parish was mentioned in the Domesday Book as Lelinchestane. In the 12th-13th century the place was known as Lillingeston Parva and took the name of the local squire, Dayrell, in the 14th century.
The church is usually open and is well worth a visit (although of course the cache is not inside). Be sure to see the brasses of Paul & Margaret Dayrell, 1491 and Richard Blakesley, Rector from 1473 to 1493. Replicas of the brasses are available for brass rubbing at £1 a go. You can also see the very impressive tomb of Paul Dayrell and his third wife Dorothy.
Outside the church is a small churchyard which is still used today so please respect it. This could mean problems on a busy Sunday. The cache is a small clip-lock box. There is no need to disturb any of the monuments in the churchyard, nor is it buried at all. Children as well as those blessed with more height will be able to reach it. That's all the clues you will be getting.
As there are some houses adjacent to the church I would suggest night time caching might well raise unwelcome suspicions.