You could write directly to the ward for immediate attention, and send a copy to the Trust HQ - address is probably on their stationary, or the Internet.
The Hospital Administrator oversees all staff so him/her I guess. I would also sent a letter of thanks to the head of the ward or department in which I received the treatment so that they know that they are appreciated.
Write to the chief exec. Do not do what one of my patients did, which was write via her solicitor , and he barely glanced at it, sent it down to the PALS office with the other complaints letters, where it was read properly, and re-routed back with the compliments!