Universal Annual pass benefits for UK guests

Can anyone help with annual pass info please?
We are staying 5 nights at HRH and have 14 day UK Universal park tickets (which include Volcano Bay) Is there any benefit to at least 1 ticket being upgraded to an annual pass -
What would be the benefits
Any idea if the cost to upgrade
Can we do it whilst we are there, possibly on a day we visit before our stay to take advantage of the benefits

Check blackout dates. I’ve been planning to get a seasonal pass if there’s a room discount but Volcano Bay is blacked out on our dates. I’ll still be ahead getting the 2 park one and buying a 1 day ticket to VB though. I’ve already got DS’s ticket and if there isn’t a discount I’m just going to get the U.K. ticket for myself too. I assume there are some discounts on food and in shops but I haven’t looked into it as I just want the room discount. Maybe free parking? I don’t know though, again that’s no interest to me because we’ll uber.

I calculated that it is about £30 more to upgrade from a 14 day, 3 park ticket to a preferred 2 park ticket. This gives you 10% discount on food and some discount on special event tickets plus maybe some room discounts .