Advice on a charge controller please :)

[Jonathan]

46v for 24v charging

A nominally 24V (72 cell) panel can output close to 46Voc in bright sunlight, so the controller would have to drop the voltage from around that to about(!) 10.5-15V. It depends on how they've designed the converter...

... my thinking was seeing a real 250 watts from a 250w panel would be pretty rare in this country and on the occasion that it did it would just be wasted... wouldn't make it to the battery through this charger ?

The controller will either overheat and cut-out, or if it has a few more brain cells it will regulate the power input to only what it is rated for, so 200W. Solar panels are rated at an irradiance of 1000W/m^2, which is typical in England in the summer.

you win some and you bin some :)

Well let me know if you bin it ;)