All signs are pointing to at least 1 interest rate cut later this year so I think fixed rates are coming down but it doesn't look like rates will be going up for a while now. Trackers are good in this environment because they will go down if the base rate drops.
Having said that, fixed rates are good to guarantee that you will always pay the same amount each month no matter what happens.
We're in the process of remortgaging with Woolwich, they're doing a 0.69% or 0.89% above base rate tracker (currently 5.69% or 5.89%) but the lower rate comes with, I think, a £599 fee, I think, the higher has no fee.
Be aware, if you switch to another lender they'll need to go through a verification process and get their legal team to do the switchover so it could take 6 weeks or so.