Hal's are pretty rare, though I think they're a great preamp. I sent you an email regarding info I received from Rega. I sold my Hal and the manual went with it. The buyer was an Agon member so maybe he'll see this and help you by sending you a scan. Below is a URL for their Exon 3 page. If you have the Hal, your is probably the Exon 1. You should contact their service department, they may be able to email the pdf for the Hal and Exon 1.
http://www.rega.co.uk/html/exon.htm
http://www.rega.co.uk/html/exon.htm