I am hit with VAT and import duties of about 35-38% every time i import from Canada to DK (we have 25% vat) , but I am told that the UK and Canada have an agreement whereby you can pay a very low UK VAT (but you may have to pay CA VAT, instead).
Some small companies will "fudge" the declared sales price to lower your taxes and duty. VAT is charged on all goods and services + shipping costs. If the item is a repair or upgrade, technically you have to get a form filled out when you send the goods back to Canada, so that the UK authorities know that this is not a new unit when it is shipped back to you and do not tax that. This rule is EU-wide.