Hey 666, well done on passing your test. As you will see, you get lots of opinion here some relevant some not!
The real answer to your question depends on whether you have passed for a JAR licence or a UK National licence. With the JAR licence your Single Piston Class Rating has no weight limit so, if it has one piston engine you can fly it provided you get the required difference training for tailwheel, VP prop, retractable gear etc as appropriate.
For the UK National licence there are more severe limits. If in doubt ask your instructor for authorative advice.
Happy landings
3 Point