I think this is going to be a problem. The item was for pickup and now you have the buyer organising a random courier. You will have to pack the item extremely well, which may incur additional costs for you. The courier will not take the item otherwise.

There's nothing to stop the buyer opening a case for "Not as Described" and claiming that it arrived damaged or was not in the condition advertised.

Personally, I would cancel the sale with the reason "problem with buyers address". 

I think there have been some scams against sellers who sell high priced items and where buyers have arranged their own courier - others on the boards will clarify.

Also, there is a 21 day hold on funds if you are a new or intermittent seller. The funds can usually be released by inputting the tracking number, but I have heard that there are still issues sometimes.

What is the buyers feedback left for others like?