Import costs, carriage costs apart, are ABSOLUTELY EXACTLY the same from anywhere in the world. They do not change because the charges are the ones levied by HMCE, NOT by the exporting contry.
Charges are VAT, plus a small % duty, plus a handling charge. On items to something like £200 the total is around 30% of ALL payments made abroad - the variation in the % is due to the handling charge - huge % for cheap items, very little for expensive ones - actually around £10 irrespective of what or value of the import. There is no longer any tax-free allowance - everything imported, in theory, gets taxed somewhere.
I import stuff a few times a year and about 30% get missed by UK customs.
UK laws are now pretty much inline with most western countries - the great majority insist on foreign businesses levying their VAT in the foreign country.
If a business seller abroad is not registered for UK VAT, you are likely to get charged VAT twice - once in each country, or the item may be sent back to the sender.