Does anyone know if you have to pay custom duties

It seems pretty clear on the  government website

"Transfer of residence relief

Transfer of residence (ToR) relief is available when you:

• transfer your normal place of residence - it allows you to import your goods, including animals and means of transport, with relief from import duties and charges
• are a student coming for full-time study
• are moving to get married or enter into a civil partnership
• are moving following your marriage or having entered into a civil partnership

The relief exists for those persons who wish to make the UK their normal place of residence. This means the UK will be your main principal home. The relief is only available to ‘living persons’ and their personal property. It is not available to trusts, companies, corporations, associations, groups or organisations.

There is no relief for goods imported from secondary and holiday homes.""

So -

- if bringing goods back from holiday home - you should pay tax

- if moving permanent home back to UK - no tax