There is no right answer here, you seem to understand the difference between the two and the relative merits of one over the other.
The basic question is do you want to pay a premium for the luxury of a fixed rate and the security that comes with it, or do you want to take a risk with the tracker option.
Without a complete understanding of you circumstances nobody else can offer any real advice.
The most important question I thin you should ask yourself is....
can you afford the repaymentts if they increase over the next couple of years?
..... as you face the risk of this happening if the _base_ rate increases, and it wouldn't surprise me if, when the _base_ rate does go up, fixed rates increase too. So calculate your payments on the current tracker rate, and then do a few more calculations assuming rate increases, see how this affects your repayments, and see how comfortable you are with it.
Not sure how helpful this is, but withgout a full factfind I can't really offer you better advice.
This goes for anyone else in a similar situation, it is not necessarily an easy decisions, and if full & complete advice is what you need, speak to a mortgage adviser. Also remember that the larger the loan, the bigger an impact any interest rate changes will have on your monthly payments, so those with
large mortgages should be particularly careful.