Great to hear that you are planning to drive on the Wild Atlantic Way! You will know that this is the world's longest touring route, at 2,500 km and indeed, there are some breathtaking sights along the way. The route passes through 9 different counties: Donegal, Leitrim, Sligo, Mayo, Galway, Clare, Limerick, Kerry and Cork. There are 3 airports along the WAW that you can fly into from London - Cork, Shannon (in Limerick) and Ireland West Airport Knock (in Mayo).
I would suggest that, in order to really get a feel for the 'real' west of Ireland, you should try to explore as many of the nooks & crannies of the WAW as possible - these are where the most stunning views are, with lovely villages & amazing stories to be heard - just off the beaten tracks. So, you could divide the WAW into 3 - maybe in accordance with airports. If you decide to fly into Cork, you could easily spend 6 days driving through all the peninsulas and winding roads of Cork or Kerry & Limerick! The same applies to Clare & Galway (flying into Shannon), and Mayo / Sligo / Leitrim and Donegal (flying into Knock).
Some counties are huge and have so many peninsulas to travel up & down, e.g. Donegal, Cork and Mayo.
For example, Erris is a vast region in the north west of County Mayo, and includes the Mullet Peninsula. Erris has been voted the best place in Ireland to go wild! You could easily spend 2/3/4 days travelling through the entire region - we have four lighthouses, Ballycroy National Park, several looped walks (on beaches, on cliff edges, by lakes), a heritage centre, award-winning restaurants, deserted islands, adventure watersports, and the list goes on ...!
It won't be an easy task to decide on your route . . . go n-éirí an bóthar leat!
(translation: may the road rise with you / good luck on your journey)
Tourism Officer, Erris Beo