There are no restrictions on importing antique firearms into Canada. Get the seller to put a letter in the pkg saying it's a legal antique and "pre-1898 antique" on the customs declaration and that's more than sufficient for importing into Canada.
EXPORT from England is another story and I don't know the answer for that. I tried to buy a webley revolver from a dealer in the UK but he would not entertain shipping to Canda although he would ship to the USA. From conversation with him I "suspect" that there are no restrictions on exporting legal antique firearms from the UK, BUT I do not know what constitutes a legal antique in the UK.