But I think the main thing that causes warm / cold weather is the airflow and the direction it comes from.
From a low typically we get tropical maritime airmasses over the UK from the Atlantic - so in the winter warmer and wetter (than it should be) and in the summer cooler and wetter (than say the continental Europe). The sea acts as a big regulator in other words.
Around a high, due to the clockwise spin, this typically drags in colder arctic air in the winter, from Siberia direction. This air tends to be dry and cold. In the summer, the Azores high may build up and due to the position of the high tends to bring the air in from the continent (from the E or SE), which at that time of year is typically hot and dry. This is why the SE corner of the UK is typically hottest in the summer. In the winter the SW corner of the UK is typically warmest as the airmass hasn't had time to 'cool' over land after passing over the relatively warm Atlantic. We tend to get masses of snow when these two air masses bump into each other, so you get the warm, humid air from the Atlantic meeting the cold dry air from Siberia....
Low pressure areas tend to be further south in the winter due to the quasi stationary polar front moving south (where the Jet Stream tends to exist). In the summer when the QSPF moves north there is the chance for the Azores high to build and hence the possibility of a run of stable warm weather. Highs have the effect of blocking the lows, which then tend to move around to the north.