What kind of steam trains are still preserved today in the United Kingdom?

Please define "preserved".

There are hundreds in museums and dozens more out on the tracks. They range from narrow gauge locos to record breakers like 'Mallard'.

Note: A train is a locomotive / engine, plus carriages and/or wagons. There is a big difference between a train and a locomotive / engine)

old ones

just look up YORK TRAIN MUSEUM ...one of our greatest ...the flying Scotsman has just been renovated and is running again ....also look up the blue train

The Steamy McSteamface kind...

There are at least 50 preserved steam lines operating in the U.K. They are huge tourist attractions. The most well known id the Bluebell Railway in South East England
www.bluebell-railway.co.uk