With the tip sites you have to be aware that anyone based locally will have arrangements generally in place to dispose of their arisings - whether it is a yard, regular tip sites, or a commercial deal (preferential tip rates, selling on for biomass) - as described above.
Where they come into their own often is to anyone working outside their usual area who need somewhere handy to tip. As an example, I've seen tree surgeons around here from 10+ miles away and for them to fill a tipper truck, return to their local area, tip and back to the job for another load costs (20 miles van use, 2 hours labour costs for driving, job takes 2 hours longer - could be into a 2nd day, any tip fees) and then having a local tip site becomes a viable option.
You are then competing with all other local tip sites. Point I am making is that registering on the tip sites isn't going to bring you a driveway full of logs - people will be in contact as and when it is necessary for them. Great to have an introduction though, someone might be reading this Gloucestershire way and remember seeing your post,
Also to note as above, people see logs as a resource, the home owner with the tree sees 2m3 of oak, then pops into B&Q and does some sums, the oak wood will pay for the tree surgery! (yeah....) and decide to keep the wood themselves to sell on for massive profits - you are more likely to be offered softwoods and gnarly bits... I'd guess I'll get 75%+ as softwoods and only a small portion is hardwoods. (note: making a fortune from your garden tree... take away your time to log it up / pay for the tree surgeon to do so, perhaps buy a chainsaw (+ safety gear) and axe if DIY (or log splitter hire), store in the garden for 1 year+, deal with facebook ads / gumtree, the value of your time eats away any profits pretty quick - often far more profitable to do a couple of hours overtime in your regular job.. so a lot of homeowners are keeping their hardwoods with that thought process)