I did another test today - the silicon hose I ordered arrived in the post this morning and since I wasn't planning to brew today I figured I may as well check it all fits. Otherwise mainly the same as last time.
I ordered 2m of 8mm ID x 12mm OD silicon hose. This is slightly smaller than the 9mm ID PVC tube I used before so I wasn't certain if it would fit over the tap on the kettle but it's fine - unlike the PVC stuff, silicon is pretty soft and supple even when cool and doesn't really change as it warms up. It's also a better fit on the pump inlet/outlet. Still, pipe clips all round just to be sure
One thing I did change was to add some lactic acid into the water, mainly to stop my stupid hard water turning my kettle into a giant stick of chalk!
I can't quite bring myself to cut a hole in the lid of my kettle - I don't actually have a drill big enough anyway though I'm sure FIL will have something suitable in his workshop. For now I've used a box clip on the rim of the kettle to prop the lid open - actually makes it slightly easier to remove the lid if I want to check the grain temp with a thermometer, compared to feeding the pipe through a hole in the lid. I figure a towel or two over the lid will cut out most of the heat loss by convection through the gap.
So, all looking good - next brew day planned for Tuesday so will give it a whirl for real then (what's that expression about no plan survives first contact with the enemy... )