Many thanks for these replies, much appreciated. Yes, that year was 1898 and the 2 kids ages were at 1902, but I am guessing they were not with him. I have no other info., so don't know why he was there; maybe looking for a new start etc. etc. No known family in the USA.
UK access to some sites hasn't worked, eg burials A-Z only stuck on "A", like the newspaper websites. A needle in a haystack job I know, but let me know if anything turns up. He could have remarried I suppose. His original work in the UK was carriage trimmer, probably at the big Doncaster railroad industry.
A year or two ago, for fifty dollars, the library sent me an official certificate to say that a death certificate had not been found. The UK admin just states that he was "of the City of Buffalo in the United States of America".
The surname is not rare, and there is a UK passenger list entry for a "Mr.A.E.Robson, year of birth 1868, occupation builder. Left Southampton UK on 31st March 1900 to Durban (Port Natal). The name and birth year fit, not the occupation, but who knows!! There is a Buffalo in South Africa, so could the UK admin be a human writing error (!) I gather records in SA are hard to find, but I may put out an APB. My thanks again, and do keep in touch if anyone comes across anything. Regards to all. Mike.