I can't recommend getting a visitor's visa strongly enough. It's a pain, but after what happened the first time I came to visit my now husband I would never take the chance of being turned back at the airport.
Two years ago last month I came to visit for 7 weeks. At that point we had been talking on skype for several months and were ready to meet each other in person. At that time I was 57 years old, on solid ground financially, and absolutely unaware of any of the immigration issues in the UK. I was blindsided when the IO at Heathrow started asking more detailed questions and then had me sit and wait until he could get another IO to take over. I was absolutely honest that I was coming to meet a friend and there was the possibility of something further, but we were just meeting at this point. The second IO called my now DH to check out my story, and continued to ask me pointed questions while I stood there at a complete loss. Finally she said she was letting me go (grudgingly) and would be watching to make sure I left the day my return ticket indicated. I was given a visa for the exact time of my 7 week visit.
I had no plans to do anything other than visit for 7 weeks, I had credit and debit cards with me, and about $15.00 cash in my wallet. When I asked the IO why I was flagged for further questioning she said it's because I didn't have much money with me - only the 15 American dollars. At the time I had no idea why she thought I would I have more US cash with me on a trip to a different country, but evidently credit and debit cards are meaningless without bank statements to verify funds. I simply had no idea I was expected to be prepared for all this. It was humiliating and probably the best thing that could have happened to me, because I knew just how serious the anti immigration attitude here is and, thanks mostly to this forum, did everything by the book from then on.
The most embarrassing part for me was when this woman told me - in a rather condescending manner IMO - that, unlike me, my "friend" didn't have any romantic notions toward me (I had simply said I didn't know, but it was possible - he was far more circumspect). I walked away feeling pretty darn pathetic, but my poor future husband had to wait for me not even knowing if I was being allowed to continue on or if I was on my way back to the US because I wasn't able to get a signal to call him!
Not a lot of fun, but at least I was let through and able to continue with my plans. I now realize I was lucky despite how humiliated I felt at the time.