Hi I have had a breakthrough with the Hopkins.
I found the will of the brother of my Samuel Hopkins born in 1795.
George Hopkins born in Curry Rivel in 1790 was in the Royal Navy and his 1811 will proved in 1813 names his parents Thomas and Martha and his brother Samuel.
It also shows that as I suspected Thomas Hopkins and Martha came to the London area with their family.
Probate of the will shows Martha Hewlett/Hopkins died in c1811-1813 but I can't find her burial.
Thomas appears to have remarried another Martha (widowed Martha Kettle) in 1814 in Walworth and died in 1820 being buried in Locks Fields Chapel that year.
What is intriguing is that George names his grandfather Thomas Hopkins senior (born in Curry Rivel in 1720) as having left him a legacy of three hundred pounds.
Now this is an extraordinary amount of money and so Thomas Hopkins senior must have been quite wealthy. He is evidently the Thomas who died in 1799 in Curry Rivel, or so I assume.
The executor of the will was a Samuel Maitland though who was of Walworth. I have tried to find out about him as I assume he was a relative who also moved to London, but I can not find anything out about him! Feel free to have a look.
It is all rather surprising as George's father Thomas I now know to have been a day labourer in Curry Rivel in 1772 when he applied for settlement in Compton Dundon.
So how was Thomas senior 1720 so wealthy with Thomas junior 1751 being so poor?
A mystery to be solved.
I suspect that Thomas Hopkins junior born in Curry Rivel in 1751 was not reliable or the black sheep.
In his marine son's will, George Hopkins leaves the £300 left to him in his grandfather Thomas senior's will to his mother Martha, not his father. And if she died then to his younger brother Samuel, not his father.
It is very interesting. George's ships are also listed in his will and he was on the Mindon and died on a hospital ship. I rather assume that he was injured in the July 1811 event. See
https://en.wikipedia.org/wiki/HMS_Minden_(1810)
£300 is worth £10,000 today but we know Thomas had at least four grandchildren alive at his death.
There were Maria, George, Samuel and one of the elder brothers.
I do not know for sure which one was alive but George refers to Samuel as his youngest brother in his will so there must have been at least one other alive at that time.
Presumably Thomas would have left all of his grandchildren this amount as they were all underage at the time, so he presumably had at least £40,000.
Sadly the Somerset wills are lost in the main thanks to a bombing in 1942 so we may never know

All for now and thanks again for the replies,
Jon