Hi there-I had this problem. I first came on my spousal visa in January 2005 and went to apply for IRL in late December 2006 in person at Croydon. I posted on the forum in 2008 about what happened (see below). Well done on keeping your boarding pass-I was not so lucky. Having said that, I did get the IRL at the later appointment and am now a British citizen-but had UK Yankee been in my life then, would have flown direct into London!
Hello-
I've just joined the forum and thought I would reply!
I flew into London with Aer Lingus via Dublin and yes, you have problems. I went in person and then had to return about a week later with more proof. No kidding, the woman wanted to see my boarding pass from Dublin. When I replied that I didn't keep it (it was two years ago!) she said I should have.
So, I:
Phone Aer Lingus and they gave me an email with a confirmation code that I was on the flight. They told me then (this was over two years ago) that they didn't do letters with this information.
Got a letter from where I had an interview during the time I was in the country but needed proof, signed by headteacher.
Got a letter from my employer stating when I was employed with them and from which point.
Got a signed letter from my local library with proof of my joining date (I'm a librarian-so I joined the library early)
Found any other letters, etc. that showed I was in the country.
Brought along my NHS form I got when I re-registered at my new UK address.
I came to London via Dublin in January but didn't have a stamp until August as I hadn't left. It was a hard sell at the first window and then when I went upstairs the person seemed unsure. I had no idea that this would be a problem-I would have never flown via another country had I known this. You'll need lots of concrete proof that you were here. Don't cry either-the stress of the first meeting put me over the top and I was told 'crying won't get you anywhere!'
Hope this helps!
K.S.