In 1851 living in Helpston was another Lilley family, headed by John age 46 born Haddon Hunts, wife Mary 40 born Helpstone, and 7 children 20 - 3 years of age, all bar the second who was born at Stilton Hunts were born at Helpstone. So he appears to have stayed in Helpstone after his marriage in c1830.
Haddon is only 4 miles from Castor where Alice wife of William was born.
I don't believe in coincidences!
There's a John Lilly baptised in Haddon on 24 Feb 1805, son of John & Ann. John Lilly married Ann Green in Bythorn, some miles further south, on 3 Dec 1798, where they baptised a daughter Ruth on 7 Apr 1799, and there are then no further Bythorn baptisms to this couple. John & Ann baptised William in Haddon on 22 March 1801, but he is, I feel, too young to be your William. A Ruth Lilly married in Haddon in 1821 which adds to my supposition that the Bythorn couple moved to Haddon in c1800
A John Lilly was baptised in Bythorn on 10 Feb 1779, son of Richard and Elizabeth, which looks to be the John of the 1798 marriage.
Bear with me, you'll see where I'm coming from in a moment!
Richard and Elizabeth had a number of other children in Bythorn, including a William who was baptised on 12 Feb 1786. There's no marriage in Hunts of a William Lilley that could be this one. Nor is there a burial of a William Lilley before 1800 which is as far as I can go in Bythorn and Haddon, or anywhere else in Hunts for that matter.
So to summarise
- your William Lilley was living in Helpstone in 1841, not born in Northants
- a John Lilley born 1805 at Haddon Hunts moved to Helpstone in c1830 and was still living in Helpstone in 1851
- this John was the son of John Lilley born 1779 at Bythorn
- John Lilley born 1779 was the son of Richard Lilley, who had another son William born 1786 at Bythorn
I think William in Helpstone in 1841 may have been the uncle of John in Helpstone
Pure speculation! Can't prove any of it as his marriage entry says he was a resident of the parish of Helpstone. But if you go through the parish registers of Bythorn, Haddon and Helpstone they may come up with something more concrete
Regards
David
PS Can't understand why I can't see John and family in Helpstone in 1841!
PPS Can't understand either why you have crossposted this same request on a number of boards without mentioning the information you already knew (1841 census, marriage, children), or have been given in previous threads eg I see some of the above relating to Haddon (but not Bythorn) was given to you last April. As was the burial date and age that Sue gave you. I could have saved myself a couple of hours work. You're not encouraging me or anyone else to spend much time on your requests in the future. I don't expect to have to plough through someone's posting history in order to fill in the blanks.