I know this simply proves how clueless I am when it comes to my bug, but I’ll only learn by asking questions and trying things out myself! Almost cant c out the window cos the blades r so worn. Nipped to Halfords and asked if they stocked suitable blades. Have the blades but cant get my head round how to fit them. I have the old one off, simply released the little spindle from the cup shaped holder but I’m stuck. Haynes manual talks about the wipers but only how to remove and replace the motor. They must assume no-one is as stupid as me obviously. Please help! 
put correct sized clip onto blade then stick wiper arm through one of the holes in blade move blade so one side of arm on each side of bar in blade and move blade away from windscreen till locating tab locks
if your really stuck take them back to halfords they will fit them free but if you study your blades and wiper arm you will suss it out
Simon
Have a rough idea after looking over them but the guy tried to tell me I needed the " W13" type blades but they were huge so I bought the “W10” blades which were almost exact same size as the old ones (give or take a centimetre). Could I maybe already have the wrong size blades on the car which is maybe causing some confusion??
The Halfords listed sizes for cars are regularly wrong. Bought some for Anne Maries car last week and the listing was at least 2 " longer than required.
If your existing ones are the same as the new ones and you are happy with the sweep area for vision then the 10’s should be fine.
Bob
Cheers Bob, yeah they seem fine! Just need to wait for the next down-pour to be sure, not that I’ll need to wait long for that I’m sure.
If its a flat screen Beetle then the blades should be 11 inches long unless its before 1971 then they where 10 inches but the 11 inch ones will fit and are more easily available. If its a 1303 curved screen then you need 16inch blades
Simon
Hey! it’s a 1975 South African import with a flat screen. The blades are fitted and seem ok. Jobs a good’un 
If I don’t see you though the week, I’ll see you though the window!