Speaking only about the financial side.
UB do not currently offer a tracker mover product like other lenders do. They will offer you a 10 year tracker at ECB + 2.5% up to your current loan value. You will lose your current tracker rate, or any right to revert to it.
You will need 20% deposit, which you should have based on equity value you mention.
Other major costs are commission on sale (between 1% and 1.75% plus vat, depending on area, sale value and agent), stamp duty and legal fees on purchase.
Your biggest challenge will be timing. It is likely you will need to sell your current home before you buy, unless you can buy subject to sale. Again depending on area / demand.