I had a few hours to myself this morning before I went to work, so I thought I'd have another go at knocking the seized pistons out of the 2.5 Pi engine block.
I started with a piece of wood and a club hammer and this worked well on the first two pistons, but then splintered and broke up. I then found a length of one inch box section and used an old brake calliper piston of a nice round shape to sit level on top of the pistons, before placing the box section on it and then hammering with some force.
This engine must have been seriously overheated in its lifetime as every piston was stuck solidly. It took some force to eventually knock them all out. Number four piston was particularly seized and I didn't think it was going to come out at all. Eventually, though it gave in and by the time I had to go to work, I had managed to get all six out. The downside was that not one of them came out without damage, but the block looks ok and may just get away with being honed. If not, it's not a big deal as it can be bored to plus 20 thou. A good mornings work though and the next stage now, will be to separate the remains of the pistons from the con rods.