If I'm being honest, 250ft was just sort of a number I threw out there; such a ride could well be smaller.
My point was more; Stealth has set a precedent for the minimum height that rides can be built to at Thorpe Park. Its mere existence is something that the park can use to their advantage if their request to build a similarly heighted or slightly taller ride encountered obstacles.
One potential point to raise is that I think the scale that a UK height record breaker would need to get to in order to gain the height record depends on which source you go with for the Big One's height. RCDB says 213ft, which is only 8ft taller than Stealth. Blackpool says 235ft, which is a bit more noticeably taller than Stealth. Personally, if I were Thorpe Park, I'd want to err on the side of caution and top Blackpool's own claim; if they built a ride of, say, 220ft and marketed it as the UK's tallest coaster, Blackpool might well make a fuss, or they might get reported to the ASA for false advertising Wicker Man-style. As much as RCDB says that the Big One is 213ft, your average punter watching both parks' adverts may not know that, so they could quite legitimately ask "How is Thorpe's new coaster the UK's tallest at 220ft when the Big One at Blackpool is 235ft?". Also, I feel like a 235ft+ hyper coaster would give off a greater impression of size compared to the rest of Thorpe's lineup than a hyper that only just pips Stealth in height, which would give more gravitas to the park's inevitable "UK's tallest coaster" marketing campaign and the ride's actual record in the eyes of the general visitor.
Another thing I think is worth pointing out is that a bigger hyper coaster also opens itself up to stealing other UK records besides height. Take Shambhala at PortAventura as an example; that ride is 249ft tall (14ft taller than even Blackpool's Big One height claim, and 44ft taller than Stealth), reaches 83mph (3mph faster than Stealth) and has 5,131ft of track. If Thorpe built a clone of Shambhala (hypothetically, of course), it would be the tallest & fastest coaster in the UK, and it would only be 366ft short of the European length record of 5,497ft (due to the Ultimate's likely demise, the Big One now holds this). I certainly think a ride that gains all 3 major UK coaster records (tallest, fastest and longest coaster) is quite doable, personally. Taking B&M as an example (I use B&M as they've built far more hypers than any other manufacturer); excluding the giga coasters, they've built 2 hypers that top the billed UK height record of 235ft (Silver Star and Shambhala), 3 hypers that match or exceed the UK speed record of 80mph (Nitro, Diamondback and Shambhala) and 3 hypers that come within 200ft of the UK/European length record (Nitro, Silver Star and Behemoth). I don't know about you, but I think "tallest & fastest in the UK and longest in Europe", or just "tallest, fastest and longest in the UK" for simplicity, would be a pretty big deal, and I think Merlin could have an absolute field day with the marketing; they've got those records as their "compelling proposition", and surely the raw size of the thing would be a "killer image"? (Those are the 2 requirements for any Merlin ride to get considered for the green light, if anyone's wondering)
In terms of planning restrictions; I'm admittedly unsure how high Thorpe could feasibly go within the 500ft ceiling, but if Wardley of all people says that a hyper is doable within Thorpe's planning restrictions, I'd certainly be inclined to believe that it can be done!
