Half term, MawBroon? That has even less to do with the subject than plimsolls!
Wellies, as suggested by lemongrove, are so sensible for this time of year and, paired with a tasteful onesie - zebra, polkadot, zigzag etc - you have a cosy outfit.
Lesley you will have the last laugh in 20 or 30 years time, when your colleague has developed arthritic knees due to cold draughts, while you still skip blithely along (unless the fags get you first, of course.)