is it cost effective to move from hsbc 3% to 2.79%

hi i borrowed
51k over 12 years
paying 421 per month back
its a life time tracker at 2.49 + .5 boe rate so 2.99 %

i can over pay and switch to any mortgage apparently.
so hsbc now offer a 2.29 + 0.5 boe = 2.79 % tracker

how much will i save per year if i switch?