First of all you need to decide what visa you need. Then you will need to faind out what you need to do to fulfill the requirements of that visa.
There are many visas to choose from & it can get quite confusing. We came over on a Former Resident Visa, as my dh lived her from 1972-1989, but was not a citizen, hence he had to re-apply. We had the option of 3 different visas. We went for the one that almost guarenteed our entry.
We didn't need a certain amount of money to enter, but we did need enough to live on for 2 years, without claiming from their benefits system. We claim their equiv of child benefit, but this is because we are now permanent residents. If you do not get a permanent resident visa, you can't claim & sometimes can't work or get a mortgage, so read up carefully, or use an immigration agent (I have the number of the one we used, will be pleased to pass on)
We put our application in Nov 05,
It was accepted Feb 06 & we got here June 06.
THis is the official site for the immigration office. HERE
HTH, there are lots of people around on the Living Overseas board that will be happy to help. There are long threads of advice there too. Feel free to ask anythng, we will do our best to advise.