Yes, there are similarities there. But there are similarities with other locations as well, and GRRM has said his primary inspirations for some of those locations is different (Dorne has a few nods to Cornwall, being a peninsula located at the southern end of its landmass plus the name, but it's primary inspiration is Moorish Spain).
I'm not sure about 'most things', but yes, there are strong influences and inspirations from real English history, amongst other factors. I was just puzzled because in your original post you said:
Which is not the case at all, as you later say. Moorish Spain, the primary inspiration for Dorne, was not located in England, for example. The Westerlands has similarities to Wales in terms of terrain (hills and low mountains), resources (gold and silver, compared to the real Wales's impressive coal resources and a small amount of gold) and location (in the west), but also major differences: the Westerlanders are not fiercely nationalistic in the same way the Welsh were/are (a trait more strongly found in Dorne) and are one of the more populous parts of the continent, able to field one of the largest armies, which was not the case of Wales (which has always been somewhat under-populated considering its size).
The point I was making was that Martin drew a lot of inspiration from real-world history, but also mixed and matched things up. Robert Baratheon is partly influenced by Henry IV, for example, but his later fat indolence is a nod towards Henry VIII whilst his thunderous voice and hunger for combat is actually based on the totally-fictional King Richard IV (played by Brian Blessed) from the
Blackadder TV series (!). This keeps things more interesting. If
ASoIaF was really just the Wars of the Roses mapped onto a fantasy world and we could see what was going to happen next, that'd be a bit dull. Another fantasy author named Chris Bunch actually did this 15 years ago in his
Seer King trilogy, which was much more directly based on the Napoleonic Wars. Once the until-then successful armies of the emperor invaded the vast neighbouring empire that bore more than a passing resemblance to Russia, you could predict with some accuracy where the story was going to go
ETA: GRRM has also said there's influences from completely outside medieval Europe as well. He's a big fan of the
Romance of the Three Kingdoms, and there's some echoes of that in the books (the Battle of the Blackwater has some passing similarities to the Battle of the Red Cliffs), and particularly Roman history. The vicious murderousness of the politics in
ASoIaF may actually have more in common with Roman politics than actual medieval ones.