Good luck, and don't believe this idea that someone seems to have planted in you, that all you could possibly have to offer are sexual services. That's not true at all. You can have financial safety without ever having to do that.

I'm a woman in my 20s who is (rather unusually) really getting along with older people, and I have several platonic friendships with men above 60. There's never been anything romantic or sexual about it. In my experience, a lot of elderly men just really appreciate someone who is genuinely interested in them as a person and a conversation partner, especially if it happens to be a younger woman. They appreciate someone who is intelligent, a good listener, nice, caring, and who fits their personality and preference in people. It's more valuable than sex. It's companionship.

If he's already hired help before, he'd undoubtedly be interested in you sticking around if he requires help and can afford it. It's unlikely that you'll be paid just for companionship without doing something useful practically, but companionship will be your selling point. Be aware that what seems rich to you may not actually be so by local standards, and you could probably find richer people looking for help.

Be aware that it does take emotional labour to be very pleasant and caring, but you sound like a kind person, and a caring role might come naturally. You can use this experience to make a genuine career in elderly care, which is highly in demand in places like England (and many other countries). You can get this kind of work without any experience, but people will prefer experience and/or professional training. Consider something like that at home to make it easier to find work abroad. Best thing is, you can also provide this kind of work for an old lady, and you'll probably never have to worry about sex.

Long story short, if he's paid for your trip, your best bet might be to take it and then say that you thought this whole thing would be work related given your previous association, or to backtrack and work on your friendship, then work on communicating your suitability to be his assistant/carer/au pair/whetever without him wasting any money on false expectations. If you're paying for your own trip, you might as well go and still try to promote yourself, but avoid giving him any idea that you're selling sex. (You might indeed be after his money and selling something, but that's just called looking for work.)

You might even be able to work for him from home without having to go to the UK. Be wary that living costs in England are pretty high, so don't accept work without an arrangement for your living expenses. If you're already working for him and sex is ever suggested, always politely decline and suggest helping him to find a girlfriend if he'd like.

By the way, you'd also have an easier time just looking for carer work abroad. I know someone who made a career looking after old ladies, and she lived on a gorgeous island being this elderly lady's help for years without any experience, just because she knew the language.