Can anyone help with how I might fix this? I've checked all the fuses and had the cluster out but no luck.

check tail lights work and check dash dimmer switch on headlight switch

I've checked the tail lights and they're not working either. Didn't even think to check them before. Any ideas gratefully accepted.

check tail fuse with testlight (power at both ends with tail lights on)-

is tail light relay clicking - swap and recheck tail lights -
check battery 2 fuse under bonnett -

check terminals 85 & 86 where they align in socket of fuse box - one should have power all the time other gets earth when headlight switch is turned to park & headlight position -

if no earth try another head light switch -

Thanks I'll give these pointers a try.

It was the multi function switch so had to buy a new one and fixed the prob. Thanks a lot for the help.