On the majority of goods imported into the UK tariffs don't apply because they are imported:
1 From EU
2 From FTA partners at 0%
3 From developing countries at 0%
4 Under a tariff quota at 0%
5 On a 0% tariff rating anyway
The top orange dot is the average trade-weighted MFN tariff. Preferences for FTA partners and developing countries pull this down to the green dot.
I have annotated it to highlight EU countries and some others for comparison
Note how trade preferences mean that the average trade-weighted tariff (green dot) for EU countries ends up *BELOW* NZ, Australia, USA and Canada.
The lower tariffs from 3rd countries mean cheaper imports for us.
Here is a table of average agricultural tariffs OECD countries outside of the EU, the UK/EU, and a few others for comparison. EU already in he lower half is lower still once preferences are taken into account.