Hi @craiglynes
Turn the water off at the house and open an outside tap or a lower bath tap so it drains the water out of the house plumbing and saves getting wet.
Is there an allen key hole just under the tap handle into the tap shaft.?
1 That will need to be undone.
2 The silver wall fitting will turn anticlockwise it shouldn't be on tight as it is just cosmetic maybe will come of by hand or use multigrips on the largest diameter flat edge, please put masking tape on the silver wall covers first.
3 Underneath there will be a hex nut a medium to large shifting spanner will turn anti clockwise with some force but not to much force in case the internal wall plumbing is damaged. Sometimes a hammer taping on the spanner body will work best as the smaller sharp taps will loosen in a safer manor then sustained brute force.
At that point the tape washer should come out and replace it ready for re assembly.
Hope this helps
