I'm also travelling down from sunny Northants (Daventry, in my case) - but I won't be setting off early as it's only about an hour and a half from here - call it two hours to be safe (and allow time for a cuppa on arrival!).
I'd rather travel alone though as in my experience plans to meet up part-way etc invariably come unstuck, leaving everyone late and/or rushing. Plenty of time for leisurely group riding on the way from Boxhill to Beaulieu
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Captain Slow