Depends on the value of your home as to whether or not it is worth switching.
If your property is worth more than 375,000 then it probably is as the LTV is lower than 80% and there are a few good deals around at this level.
There are many different factors to consider though when switching and you should talk to a broker about these, but at the end of the day, if it saves you money, then what are you waiting for????
If your second property is earning you money that covers 2/3 of the mortgage on your home, I don't see why you would want to sell it.