Yeah, the approach I used 2-4 years ago is basically the same. Except without the visiting.
www.pharmalife.co.uk can be used for contact details of a lot of hospitals (usually of the pre-reg pharmacy tutor, but that's still useful). They sometimes advertise summer vacation jobs on there. Also
www.hospitalpharmacyjobs.co.uk will give Chief Pharmacist name for some hospitals.
Just send off a well worded cover letter and CV. Act keen. If can't get anything paid go along for a couple of weeks unpaid (will help your case next year).