EU or UK Trademark;which one?

This can be answered (usually) by reference to cost and where you intend to sell/market. If you intend to sell only in the UK and costs are an issue ( for start ups this is often the case) then UK is your best bet. However if you can affford the EU fees  ( circa £1200) then the EU is the preferred option as a) your trademark will cover the 27 member states and b) it will prevent a German company for example calling it the same as your brand and offering the same on line

So best advice is EU. But above all get a trade mark!