With the costume at £40, and M&S p+p at £7.50 - yes, you are over the limit. Your total of £47.50 is approx. CHF 68.
limit of the goods value (including shipping costs) for an import exempt from VAT is:
- 8% VAT (the majority of items sent): CHF 62
- 2,5% VAT (e.g. books): CHF 200
I have taken this from the Swiss Post site (there is a good section in English explaining the costs/ extras/ etc.)
As well as the tax you owe, don't forget there are often 'extras' such as CHF 13 inspection fee.....