How easy to remove these without any special tools? What do I need, a big hammer and a stick?

pretty much. remember to apply a little pressure (tapping) around the cup as opposed to try and smash it out in one go

I use a flat bladed screwdriver and a rubber mallet. If you’re not happy with that a packet of biscuits and a trip to you LBS..

Yep. I use an old seatpost and a hammer.

I forgot to say a flat bladed screwdriver on the inside of the steerer tube so it sits on the headset cup then give it a tap with the mallet.

OK, enthused enough to give it a go.

Top tip get a foot long bit of copper pipe 28mm? the fatter stuff anyway saw 2 slits in one end (divide circle in 4) if viewed end on, flare them out slightly works well as pressure spreads evenly….hope that makes sense?

Exactly as whytetrash says – the softer copper will do much less damage than a screwy.

Stick and mallet works well too…

Hitting metal against maetal will produce this

and this

would a bit of curtain pole work?

just buy the proper tool, cost about £8 off ebay and saves loads of hassle. its false economy bodging it, you wont be able to use/sell the headset again, plus you have it for future jobs

One of these.

Free if you know a plumber