Thank you everyone for your help and suggestions so far. I'm sorry I didn't say where Sidney/George INGRAM was from etc...but really we don't know yet. Here's what I have:
We have a suspicion that he is the George INGRAM who married Ann ANDREWS in Horton-with-Woodlands, Dorset in 1808.
We know from the 1841/51 census that his son Joseph Henry INGRAM was born in Woodlands, Dorset in 1811, but haven't come up with any concrete evidence of baptism for Joseph yet. In all the other census returns, Joseph gives place of birth as Bath, Somerset. This is where his brother Samuel Frederick was born in 1819. We have no baptism information for Samuel, either.
Joseph Henry INGRAM's marriage has not yet been found. We suspect he married in France where his first few children were born. Thus no parent names in that regard as of yet.
Samuel Frederick INGRAM's marriage certificate in 1850 states that his father George INGRAM was a clerk. There's no "deceased" after George's name, so I assume he was still alive at that date.
And that, folks, is that.

Keith, I was interested particularly in your idea that the picture might be from an industrialist's magazine or yearbook - I had not even entertained the idea of him being involved in industry, but of course it is definitely a consideration. I will have to ask on the relevant county boards for some directory lookups - although what the relevant boards would be I have no idea. I guess Dorset and Somerset would be good places to start.
If anyone has any more ideas, please hit me with them - I need all the help I can get!!
Many, many thanks to all of you

Prue