My boyfriend (British) of 7 years (!, I know

I am currently in the UK, working on the Tier 1 visa, which doesnt expire for more than a year yet (we are getting married before it expires).
How do I go about switching over? Do I need to do the fiancee visa trick or can I just get married on the current visa?
I've been in the UK since September 2003 so coming close to 9 years, not sure if that makes any difference...
Thanks in advance, really looking forward to hearing some wisdom!