I think I guess is an Americanism that has seeped pretty thoroughly into British speech by now. I certainly use it myself from time to time and know plenty of other Brits that do.
I do too, but they never did in the series, and I'd prefer to stick to that. Of course, they could guess a figure or whatever, but wouldn't use 'guess' to mean 'suppose'. I'm even loath to have Vila use 'sod' or 'bastard' (which I have done) as it was never in the series.
Nico
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