Hello, I am Keith, one of the experts on Just Answer, and happy to help you with your question.
There is no requirement for you to make a self assessment tax return unless you are in receipt of income which has not been taxed at source. In any event, as an EEA citizen, you are entitled to a personal allowance, currently GBP 10.6K, to offset any UK income. Even our tax authorities do not like wasting time processing returns which yield no revenue! You will, of course, be liable to Swiss Tax on this income, but under the Double Taxation Treaty between the UK and Switzerland, which precludes the same income stream being taxed in both jurisdictions, any tax deducted from your dividends is allowable as a tax credit against any Swiss tax. The Treaty does not protect you from differences in rates of taxation. The notional tax deducted from your UK dividends will be at 10%.
I do hope that I have set your mind at rest on this matter.