Your first port of call should always be your own club.
If your club does not have a suitable coach, then your club secretary can put you in touch with the Invicta Coaching Group, who may be able to help.
Whatever you decide to do, remember that all coaches are volunteers - and archers.
Most of them shoot regularly and it is not reasonable to expect anyone to just drop what they are doing, even if your problem really is serious.
It is also courteous to offer to pay their travelling expenses, unless they really do live just round the corner.