Theoretically you will be charged duty on the value of the goods - which I think for a laser will be 2.7%
Other - Trade Tariff - GOV.UK
On top of that you will be charged VAT on the sum of the value of the goods, the value of the duty and the value of the shipping.
You will also be charged a handling fee from the carrier, which is free from both duty and VAT. (Parcel Force is about £10)
Gone are the days, unfortunately, where the theory is any different to the practice I'm afraid Barry.