I've not been but, in order to help anyone who might be thinking of giving it a go, here's a bit of travel information:
From the UK, you first need to get to either Knock or Dublin.
There are flights to Ireland West Airport (Knock) from Heathrow with Aer Lingus and from Birmingham, Bristol, East Midlands, Edinburgh, Liverpool, Luton, Stansted and Manchester with Ryanair.
From Ireland West Airport, car hire is available from Avis, Budget, Europcar and Hertz, enabling one to drive to Roonagh for the ferry to Clare. Alternatively, it's possible to take a bus to Westport and then a taxi to Roonagh.
Dublin is accessible by both ferry and by air (with numerous flight options from the UK). If not hiring a car, it's necessary to take the 747 Airlink Express bus to Heuston rail station. (NB: The 747 service seems to be suspended at the moment. Use the Dublin Express 782 service instead). From there it's about a 3½ rail journey to Westport, followed by a taxi to Roonagh.