I would ask around any of your local tree surgeons if you can and see what they have.
You want palm width kind of thickness trunk and cut off a nice clean branch and knot free section.
You can go smaller maybe wrist thick but the main aim is nice and clean for atleast your height. It can take a long time to tiller a nice bow and you want to be in with the best chance you can. Even guys with a lot of experience will blow a bow with more things in their favour than a poor stave.
Look for wasteland and verges along roads where trees grow all together and tall n thin. This means less branches and knots.
Also see if any of your family or friends ever come upto cheshire and I will try and get a stave to them.
I know it sounds like for ever to cut season and get to a bow but the time can be cut drastically whilst keeping you busy all the way through the build. Its even better to do a few at a time so you always have something to work on as in cut and split 2 or 3 saplings, rough them all out and de-bark, stick them in a upstairs room and get them fast drying.
There are a few quiet places where a pruning saw will get you a nice stave
Dont be thinking gardens or parks, think more wasteland and places where no one has planted lots of nice timber. Talk to any local farmers and explain what you are interested in and take pictures. See if they can help.
You say you are drawing up plans bud. We all do that and most of them are in the bin half way through the build. With experience the wood lets you know what kind of bow it will be and slaps us if we dont listen
Starting out as young as your are you will be posting bows here in a few years that put us all to shame.
Stay safe.