Canada and Spain had a diplomatic spat a few years ago over Spanish trawlers operating in Canadian waters. All the fishing boats here flew the Canadian flag in support of the Canuck fisherpeople! 
With regards to the so called transition period, it seems to me that if HMG and the EU Commission decided that we needed more time to work out the end state of BREXIT, then we should have gone for an extension of the A50 period and kept our place in the EU Council and our MEP's.
With this half arsed transition or implementation period the EU could force all sorts of shite on us. Although I guess that when we are finally independent any shite we don't like can be repealed anyway. 
Indeed. About the only concession we have is that we can agree (but not implement) trade deals. I can't see how they would be able to stop us doing so in the article 50 delay scenario you mention anyway.
As it is, the can will just get kicked on down the road with extension after extension, with us powerless to influence the things we are subjected to, because this deal is far from done anyway, with the Irish border and Gibraltar swept under the carpet in the hope that nobody will mention the fact neither of them are soluble problems as it stands.
