New to painting interior walls

Something like this http://www.screwfix.com/p/no-nonsense-9-roller-tray-set/42045

A better roller will hold more paint and make a better job, but I've always used standard cheapo rollers with decent results.

You'll need a pole for the ceilings (how did you paint ceilings previously?) and attach to the roller.

Bigger/wider rollers will put more paint on, but are heavier work.

And a brush (synthetic bristles) for edging before you use the roller (edge then roll, edge second coat, then roll second coat)

 

You can use screwfix but as the BBC says other suppliers are available. A roller is a roller, difference is usually price. You will need a brush for all corner jobs, tray can be any plastic box to hold paint that accesses the roller, standard tray needs refilling too often. Have some fun

 

Give your emulsion roller sleeves a darn good wash before you use them and give them a good rub too. This will help take any loose fibres off before you get painting. Same goes for brushes. Fibres and bristles going into your fresh paint will annoy you