My son and I went over to the Kent Mining Museum at Betteshanger Park today.
The first thing to say is that the signposting is atrocious. If you don't know the way you'll never find it by following the brown signs.
The publicity whilst it was being built lead me to believe that it would be significantly larger than it is. Perhaps the failure of Hadlow College and the subsequent takeover by Quinn Estates lead to a re-balancing? Anyhow, enough carping. The exhibits are well presented and access for the disabled is very good. A lift links the ground floor and basement. There are large interpretation panels and AV aids for those that like them, they are actually quite informative. Two exhibits did stand out, a Geordie style miner's lamp mad in Sunderland. It must have been an early specimen (unfortunately not dated) because it pre-dated the use of gauzes in a "tower" above the glass. The other exhibit I noted was a certificate issued for the use of a detector lamp, and the colour photos of the lamp burning in concentrations of firedamp up to 4%.
I took about 2 hours going around it, but I'm notoriously slow. Most people would take 45-60 minutes at a guess.