As we said, we have William Ellis b1730 in Whitechapel, but mainly from other people's trees and we wonder if there are any alternatives to this. If there aren't, then we can assume this Whitechapel lead is correct
NOOOOO!!!!!! You can't assume any such thing.
Take other peoples' trees as a guide only. Some trees show William Ellis b 1730 Whitechapel as being the William who baptised children with Ann in Woburn. Others show him as marrying Mary Clark in St Katherine by the Tower in 1749, which looks to me to be much more feasible. So there's a divergence in online trees for a start. Then the laughable tree that has Woburn and Puddington as the same William is even worse.
Then bear in mind that the IGI, which I assume is what you've been using, is far from complete for England, although Beds baptisms/marriages pre 1813 are virtually complete.
And bear in mind also that Woburn is within spitting distance of Buckinghamshire, so they could have moved across the county boundary.
As I see it at the moment you have nothing on him prior to 1752, and attempts to link him to Whitechapel are wild speculation. The fact that there's such a divergence in online trees points to the fact that no-one really knows, they're all guessing, and as happens all too often, the sheep mentality has taken over with one person copying another person's tree and the speculation is perpetuated.
Start with Woburn parish register microfilm at your nearest LDS Family History Centre to see exactly what the entries say, including the 1740 marriage of Mark Ellis.
David