Blood pressure can be controlled with medication. May take a little while to get the correct dosage of drugs for you, but once it is sorted out, takes away all the concern, and eventually even white coat syndrome.
It as at a pre-op consultation over twenty years ago, that my very high BP was detected. Yes, I do occasionally still check it at home (easy to use machine), but it remains about the same whether I do it at home, or at GP's and I can remain quite calm about it.
Do not think a CT scan will pick up the same sort of things as are detected by a colonoscopy - so go to your GP and start on BP medication, get that underway and then arrange an appointment for a further colonoscopy