Your dad is fortunate to have you supporting him.
The pills are probably Casodex, at 150 mg/day. Those taken alone as a mono-therapy are more common in UK and Europe than in the USA. Here's a link to a quick explanation of that anti-androgen mono-therapy. It may be a very good choice for one in your father's situation:
ANTI-ANDROGEN MONOTHERAPYI would also caution greatly against any surgery for him. Even radiation therapy may be of limited benefit. The Gleason 9 indicates an aggressive case that can more easily spread (metastasize). Whether it has or not, and if so whether it is detectable or not, is hard to say.
The anti-androgen pills alone aren't considered as effective as using them at a lower dose (50mg) but in combination with an injection to stop testosterone production (
leuprolide acetate (leuprorelin (UK)). Those injections can be had in 6 month doses, but they are rather costly (at least here in the US, about
$3500 USD). My diagnosis was similar to your father's, but I was only 55 at the time. We did radiation too with curative intent, then 3 years of the hormone therapy.