British Overseas Citizen - marriage planned in UK

[etarkum]

Hi, my sister has a British overseas citizen nationality. She recently got engaged to a British National living in UK for past 9 years. He is currently working in UK as well.
My sister's passport has a note on the last page that says "Subject to Immigration Control"
However she is allowed to travel to UK without any prior visa. Also upon arrival at the Heathrow (or any UK airport) no arrival stamps are put on her passport (normally for other visitors they stamp an entry visit when you arrive)
When checked with Marriage Council in London, we were informed that to be able to get a Civil marriage done in UK, my sister would need to get a Marriage visa from the country that she currently resides in (which is United Arab Emirates)
They were however not sure of the actual procedure of how to go about for the marriage visa.
We also found information that before they get the civil marriage done, she would need to reside for 9 days (actually 7 days) and then both her fiance and herself have to visit the council to give Notice for Marriage, afterwhich 15 days it will be displayed. And then from 16th day onward they can get married, provided an appointment with the Council is secured.
Our intention is:
a) We will apply for her Marriage visa from British embassy in UAE
b) Once granted the visa, she will visit UK and stay for 9 days and give Notice for marriage. And also get an appointment for marriage during Feb/2011
c) Once (b) is done, she will leave UK and come back to UAE for further shopping
d) During Feb-2011, she will travel again and get married (civil) and also bit later have her Indian wedding...

We have gathered all documents for her visa application and will actually go to British embassy to submit them... Her fiance resides with his parents (and his father owns the house), so basically we have got a letter from his father confirming that he is happy to have bride and the groom living with him...We also got other documents like bank statements of her fiance, P60 form, employment letter, photographs of them together, fiance's passport copy, chats and emails between them, etc...

I would like to get advise if the above is possible..mainly that she can leave UK after giving notice for marriage and then come back for her actual wedding during Feb next year...

Would highly appreciate your feedback...

Thanks