The presence of EU across the sea is making their exporters to comply, same goes for UK. Does not matter if you are a member or not. You can either comply with the roles or not export to EU.
Iceland complies with EU because it belongs to the EEA. It has nothing to do with "precence of EU across the sea".
UK doesn't have to comply with th EU. It has to if it t wants to be able to export stuff there.
Iceland has to comply with EU because it is in the EEA. The situation of Iceland is completely different than the situation of the UK.
The UK has to comply with the EU as much as Nicaragua, New Zealand, Namibia, etc.
If you are an exporter and exporting goods to EU you have to comply with EU rules if you like it or not and whether you are a member or not.
Iceland has to comply with the EU because it chose to belong to the EEA.