I'm not as paranoid as I used to be , but still use 3 mobiles & another device with an auto connect VPN to different regions depending on what I'm up to . I don't have the same app across devices & only activate location for mapping on Thai device . It's a bit extreme carrying 4 devices around on a trip
I maintain a UK PAYG phone number top up for £10 yearly . Having said that my Halifax current a/c & c/c no longer use OTP's & just auto open my Halifax app where I authorise payments from
Get insurance when here . If you had dates , travel insurance would then ask if you are awaiting appointments , tests , prognosis etc . Been there done that & I was declined .
Anything pre existing in UK will be accessed by insurer in event of a claim .Every GP surgery has staff dealing with medical records & disclosure