Sorry to hear that youre feeling vulnerable. What would help you feel better? Would your found family step up a bit more for xmas/birthdays if they knew how you felt, or are you ok with not doing much for those times?
If its ok with you, id like to ask more questions...
Whereabouts in the UK are you based? Did you inherit enough to buy a small place for yourself, or did you inherit any property? Or is your inheritance enough to cover rent for the rest of your life? What do you do for work?