reserving flight w/o paying?

They are not going to give a 2 year visitor MEC based upon a romance.  6 months yes, they'll do that, but 2 years?  No chance. 

It's the most economical option, but there needs to be a good reason for them to issue one.  And bf's/gf's in love doesn't stand as a good reason.

Will they deny it altogether or would they possibly be willing to take it down to 6 months?

why don't you just apply for the 6 month one outright?

Will they deny it altogether or would they possibly be willing to take it down to 6 months?

they will reduce it to 6 months if the application would be successful at 6 months.  If it would not be successful at 6 months, they would refuse.

Aeonix, listen to Garry please.  He helped me get my FLR sorted after I was denied.  Victoria and Garry are both qualified immigration advisors and know what they are doing.  Apply for a 6 month visitor visa and let the 2 year thing go.  You won't get it simply because you want it and have a boyfriend in the UK.  If it was possible or workable, don't you think everyone here who wanted to test the waters would've already done it??