I would like to know how to care for this plant but have no idea what it is. It is approimately 4ft (1.2 m) high and 6ft (1.8 m) spread. Woody stems. I need to find out about pruning, cutting back and other maintenance details. Southern UK. Thank you.
It is a Euphorbia characias of some variety, not sure which, but it has clearly been suffering drought (I live in the same area as you and fully understand why!). It is showing signs of new, shorter growths lower down the plant, which is typical of an E. characias variety.
The way to prune these is to cut down all the stems which flowered earlier in the year, right to the ground if possible, without damaging the newer, shorter growth. Although I can still see some dead flowerheads, some of the taller stems don't show signs of having flowered - even so, given the state of them, I'd cut all of them down to the ground, leaving just shorter, newer ones low down, or cut them down to where's there's new growth nearer the base. This will at least improve its appearance, and you will still get flowers next year.
A word of caution though - wear gloves and keep your wrists covered. These plants produce a milky white sap and it can be highly irritant on the skin of some people, so keep it off your skin. And then water it, if you are able to, with a couple of gallons applied (steadily and slowly) to the soil at the base. Or leave the hose trickling at the base for an hour, if you don't have a hosepipe ban in place.