How to order a route for a 3 month Ireland, Scotland, Englan

How to order a route for a 3 month Ireland, Scotland, England summer trip?

I'm planning a 3 month (Ireland, Northern Ireland, Scotland, Wales, and England) trip (June 15-September 15) this summer. My question is how to ORDER the destinations? I'm coming from Iceland (where I will spend May). The flight lands in Gatwick, and on June 15, I have to decide whether to enter the UK, and start my 3 month trip in England, or the 2nd option is to change planes, and catch a flight to Dublin, and begin my trip in Ireland. By the end of it, I will see the same destinations, it's just a matter of ordering?

Option 1, means I will spend June in England, July in Scotland, and Ireland through August, and September. Option 2 allows me to see Ireland in June, and England in August, and September. Which way is best? Weather should be good either way, so when is the best time to visit Ireland? June, or August/September? I'm looking to avoid the crowds no matter where I go, of course. I'd like to spend a good amount of time in the Scottish highlands, as well as other natural areas in Ireland.

That's the point of the trip. Natural scenary, and landscape photography, (in clear, pleasant weather).

Thanks

Most of Ireland hotels offers online booking....!!!! so not to worry...!!!