Stephen, thanks - good advice, although if I can get close enough I'd rather the 120-300 regardless of what light's available as it provides more exposure options and at f/5.6 the image quality's a little better than the 100-400mm.
Larne, I'll let you know - we thought about going to touring cars but decided on seeing as much of the BSB Series as we could manage this year. We're planning on Oulton Park, Donington, Mallory, Cadwell and Croft. I think we get a second shot at Oulton later in the year so if this goes badly at least I can try again
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