I have looked in the National Archives for a Will for Jane Price (her maiden name) to match my Jane Powell, but no luck. She probably was a Mrs Powell and not common-law.
Her son Horatio Nelson Powell Esq, bpt 1806, was the well known steeplechase rider c1830s-1850s. From newspaper reports he sounds like a daredevil and man-about-town; he moved to Australia in his late 50s, where his sister had earlier moved, and here he appeared to be equally daredevil and now a bit of a scoundrel. He touted himself as having been a lawyer at Gray's Inn in London, and one newspaper article indicates it's possible he was practicing in London for a period. Although it appears he certainly got around as he was still steeplechase riding around Wales and Cheltenham in the 40s and early 50s.
A 1851 census has his match living in Camden Town, in Albert Street and married (though he seems to have had several 'wives'). This is close to Gray's Inn and only a couple of miles away is the hospital at Mile End.
So, Colin, my theory lies heavier with the newspaper notice of Jane Powell dying in London in 1845 (Mile End Road, widow of late solicitor in Abergavenny), but I'll note your other Jane Powell dying in 1849 and include it as a chance. My friend's family can chase up the death certificates if they are so inclined.
Thank you for trying to find the John Powell and Jane Price marriage
The mystery remains at this point.