In October 2018, The Republic of Ireland was ordered by the European Court to cease selling green diesel to pleasure craft. It will be illegal for providers of green diesel to supply yachts with the marked fuel either at the pump or by tanker. As a result, diesel fuel is likely to be unavailable in many harbours to visiting yachts as of 2020. Most providers of marked diesel (untaxed, for use by fishing and agricultural equipment) have indicated they will not be installing white diesel pumps as the market is just too small, indicating that diesel will be difficult to obtain (Jerry can only) in many places and impossible in some.

Irish sailing organisations are petitioning the government to support strategic installation of white (taxed) diesel pumps around the coast. Three locations on the west coast have been identified: Killybegs, Rossaveal, and Dingle. There are massive safety implications if sailors are forced to sail without sufficient fuel to deal with emergencies on the exposed west coast. We will keep members posted as the situation develops.

It is our understanding that the UK has similarly been ordered to cease selling marked diesel to pleasure craft; but given the uncertainty of Brexit, there is no indication of how or if boaters in the UK will be affected.

Vice Commodore, OCC 

In 2023 Escapade took fuel by road tanker at Dingle and Galway. Both were very easy to arrange and the prices seemed competitive. That said, we were taking 150 litres... 
So if you want smaller quantities, the arrangements at Dingle were quite practical: the (quite outstanding) harbourmaster can loan you some jerrycans and a wheelbarrow and it's not a long hike to the nearest garage (unless you stop in the pub on the way). 
The harbour authorities at Galway were very apologetic about the relatively yacht-unfriendly nature of their current setup. No wheelbarrow! There are plans/dreams but these are currently unfunded. We did find that local taxi drivers were more than happy to help, though.