My passport had this damage from spilt perfume all of Covid era in Thailand and even now still. For mine it’s on many pages, including the ID page. I did many visas for Thailand and more, and lots of traveling since and it has never been an issue.
Need...maybe not? What are the covid regulations in the UK? Do they require insurance for foreigners traveling in?
Want? Depends on your budget.
When I lived in London 9 months, it was 70 pounds for an urgent care visit...7 pounds for any prescription. An emergency hospital visit was free. The amounts have likely gone up a bit...but even with insurance, it was inexpensive enough that I just paid out of pocket instead of dealing with insurance.
Or are you talking about bring your girlfriend to Thailand from the UK? Then she'd definitely need insurance as it's a requirement to come to Thailand now with insurance, due to covid.