The contract is with Boots or Dollond & Aitchison. If there isn't one in your locality, you can go elsewhere, retain the receipts & submit a claim for reimbursement. Be aware repayment can take quite a few weeks.
I was given my eye test voucher the day I passed my RT a few weeks ago. Just got the letter through today and my interview is on Friday but can't get an eye test until the 16th. Is it essential to have the eye test done before the interview? I'd phone my AFCO but they've finished for the day.