As mentioned elsewhere, Loomies does well as located in a great area for bikes, my understanding is that it is also used for some car meets and having a garage right next door also doubles as a 'transport cafe' if there is still such a thing so doesn't need to rely solely on the biker coin.
Check it out on a wet Sunday in the winter and very few bikes around, like Poole Quay, the shiny bike brigade are vital if you want to attract large numbers but obviously only during decent weather.
I really enjoy riding out to Shaftesbury, Mere, Yeovil area as very quiet roads but not many places known for bike gatherings, Compton Abbas pretty much only one that comes to mind so would welcome somewhere recognised as a bikers haunt with a decent cup of tea and a pie : )
