My dad was exactly the same. In fact probably a lower budget. For the money both he was, and your dad is looking at – i couldnt find a better deal than the Commencal Normal V-brake on Merlin. He paid just over 200 inc postage; 24 speed, 100mm Suntour forks w/lockout, disc compatible hubs (shimano centrelock), good rims and tyres, sdg bel air saddle, pedals thrown in too. Frame seems good, and a good base to upgrade when and if he wants to. He’s really happy with it.
GT’s and Spesh’s with anything close to that spec were twice the price.
If his budget was any more i’d have pushed for a merlin malt 1 though.