bzookaj, I appreciate what you are saying, but I'm still sticking to my guns regarding entrance for people previously declined a visa on a visa waiver according to the US embassy web sites:
While travelers who have been refused a visa under the provisions of Section 221(g) or 214(b) of the Immigration and Nationality Act are not ineligible to travel visa under the Visa Waiver Program, they will be questioned by an immigration official at the U. S. port of entry regarding the refusal by the Embassy or Consulate.
Having considered the matter further. It may be more in my favour to return to the UK within the 90 days - this coincides with my mother's birthday, so would by no means be an inconvenience - and would at least demonstrate my intention to leave the US an return to the UK. After returning home for a short while, I can then embark on the second leg of my journey by flying straight to Mexico.
Either way, its a gamble.
I really appreciate everybody's contributions to this thread - although I was hoping for reassurance that all would be ok, the reality is that I have every reason to be concerned. And I thank you for the reality check.
It's typical that I only applied for a visa to give me a bit more flexibility and it looks like it may screw me up completely.
I will have to make a decision on my flight out of the US and book it, so I have the ticket to show when I attempt to enter the US and hope that I will be able to convince the authorities my intentions are true.
Please wish me luck! I've got a horrible feeling I'm going to need it. Any further advice or comment on this is most welcome

