Personally I would like to see Thorpe go big. I want to see them break the 205ft mark with their next coaster, go taller than stealth.
I think a hyper coaster is something that will attract a lot of people, simply because of the staggering height. Something like Nitro at Six Flags Great Adventure, Goliath at Six Flags Over Georgia or even a modern hyper like Diamondback at Kings Island. Thorpe getting one of these rides is actually a lot more achievable than most would think, the only problem being space.
In terms of cost the previously mentioned hypers are all substantially cheaper than The Swarm (Goliath and Nitro $20m, Swarm $31m), even Diamondback is $8m cheaper ($22). Just to put it into perspective for the price of Swarm Thorpe could have theoretically built Leviathan or even Millennium Force (obviously in reality there isn't enough space).
Space is, as always, the main limitation for the park, therefore a hyper would have to be very well designed to suit the park. Goliath at Six flags Magic Mountain or Intimidator 305 are both extremely packed in coasters in terms of space, Intimidator is over 300ft and yet only takes up an area or about 800ft x 400ft, thats only ~100ft longer than Colossus and 4 times wider (really not that much for what they would be getting).
Sure a hyper would be a huge space investment but it would make Thorpe Park the best theme park in the UK and would warrant international attention. If there's one coaster design that is guaranteed to be a success and be worth the investment, it is surely a hyper coaster.
Just my opinion