I seriously doubt your two tracker mortgages will last that one!
The bank(s) would only be too happy to offload your trackers and put you on a standard variable.
One thing I'd suggest you do first is look at the market value of the two houses as they are now and try and find out if you combine the two what the market value you might be then? I'd suggest the market value for the single house may be less than that of the sum of two individual houses?
That may add further to your woes with the banks depending on your loan to value, etc., and how much of the mortgage(s) remain outstanding?