Don't I know you from somewhere Dan
In seriousness, Alton will never get a 3 hour queue in Off Peak season. As Dan said, only maybe in school trip season and end of season events. Worst i've seen it is 2 and a half hour queue for Air on a weekend July which was lovely weather and noone could actually understand why it was so busy, was very quiet the next day though.
In my opinion, the best place to start in Forbidden Valley as rides are supposed to open at 10am but due to ERT in Forbidden Valley, Air and Nemesis will be open when you get there! So do Air, then the greatest coaster i've ever ridden, Nemesis a few times, Ripsaw for a soaking and maybe Blade if you're that bored.
I would then walk down to Gloomy Wood for Duel, it is very enjoyable, I love the ride! Afterwards head towards Katanga Canyon for Runaway Mine Train which is a great family coaster, then Rapids as it will still be a short queue as it should only be around 11am. Then if you fancy getting wetter I recommend the Flume, DO NOT sit at the front lol. Why not go for a quick spin on the Tea Cups before getting lunch at the Tavern or Mexican Cantina?
Afterwards, head towards Spinball Whizzer as the queue may be shorter due to people being at lunch. It usually has a long queue due to it's low capacity. Afterwards go for X Sector to do Oblivion and maybe Enterprise or Submission. Head towards UG Land but on your way go for a ride on Hex, it's theming is brilliant!
Next up I recommend doing Rita, Corkscrew and maybe UG Swingers. Then go for a ride on Charlie but only if the queue is no more than 20 mins otherwise don't bother. You should have more time left to catch the SkyRide back over to the Valley for some more Nemesis!
Hope you have a good time!