Protein can be difficult to calculate, several suggested ways to do it, but no guarantee any of them will be correct or suit your needs. The main three approaches I've seen used from internet research are:
1) The BHF heart health diet approach you said of 0.75g protein per KG of actual body weight. Not sure on the rationale or evidence for this, haven't looked into it.
2) Kidney health advice sometimes states 0.32g of protein per lb of actual body weight. However, I haven't found any evidence that higher intakes affect kidney health unless you're in final stage kidney disease (not a doctor though, so take that comment accordingly).
3) General advice ranges anywhere from 0.8g to 2g of protein per KG of ideal body weight. As for where in that range of intake you need to hit depends on your goals, metabolism and many other factors. Traditional thinking is that maintaining current muscle and allowing tissue repair etc needs 0.8g - 1g, body building needs 2g+, regular building muscle can need anywhere in-between. However, as usual with these things, there are a million different theories on whether those ranges are correct, or what level within that range people should use.
I (probably needlessly) obsessed about this for a short while after my diagnosis, when designing my new diet. I don't know which of the above approaches is correct, but all I do know is that I'm trying to lose weight and protein helps to keep me full. I have a lot of weight to lose, but want to minimise muscle mass loss, because when losing weight a number of studies have shown that people can lose 30% or more of their lean muscle mass. I want to lose more fat than muscle, so I eventually decided to just go with 1g of protein per KG of ideal body weight as a target. In reality, although it's tracked because I use an app, I don't really worry about it other than to try and eat my target as a minimum. Seems to be working so far, I'm not hungry very often between meals, and my smart scales show I'm losing more fat than muscle, so I've settled for my approach and called it a day.