Detained at London Heathrow, trying to regain entry, please help

You should have a notice from UKBA detailing the precise reasons for being denied entry. Without knowing what it says it's not possible to give specific advice. Typically though they want to see documentary evidence that you have a reason to return to your home country such as a letter from your employer stating that you are expected back on [date], a mortgage or rental agreement that shows you have a home to return to, bank statements that show you have sufficient funds for your 4-month vacation or a letter from the person you are staying with in the UK undertaking to house you.
If you were denied entry because you did not have any of these things it's a simple matter of providing them when you apply for a general visitor visa - see http://www.ukba.homeoffice.gov.uk/visas … documents/
If the notice accuses you of using deception (paragraph 320) then you have a problem.

For a start, don't panic. I've been in the same "need a visa" position with the UK in the past and even tho they (uk border agency) are hard to get in-touch with, the system works somehow. I'm sorry to say this but you might have been a bit ignorant in thinking you don't need a visa by default!(even if it is your 4th time here) It works both ways for both countries. If your relationship is legitimate (which I believe it is) there is no reason you can't get the necessary paperwork, only hasle is time. If you feel the reason you have been denied entry into the UK is in-valid, I would suggest you appeal it (with proof some how)with the aim of possibly changing the wording so to enable the correct visa to be granted without the UK Border force asking to many questions about the initial attempted entry. There is also a company called Breytenbach's in Lodon and they deal with visa's and the like and have competent people working for them. Give them a try to. It going to be a very laborious paper work exercise this, I'm sorry to say but failing that, you could meet in France or Ireland more likely but still check the need for paperwork!