tall radiators are very good for heating the ceilings, so your spiders will be warmer than you will. A long low radiator is better for warming the room.
If you already have a radiator, decide if it is big enough to warm the room, or if you want more power. As a very rough rule of thumb, a radiator 600mm high and 1x metre wide can give about 1kW of heat. You will want a TRV to prevent the room getting too warm.
Tall radiators have to be fitted the right way up, they have a top and a bottom and baffles which cause the hot water to flow round the columns.
You will probably have to have it sprayed to your choice of colour, I expect it will be expensive. There are small painting workshops, some car repair bodyshops might do it on a quiet day, or know someone who will.
I have no idea of good brands. Look for a UK manufacturer or it might be unbranded from China.