Oh Pippa how sad. I have had a few experiences like you, first one was 25yrs ago, a much loved dog called Brandy, lovely family pet, had her put to sleep because of cancer.Next cat called Jinksy was run over right outside my house. Then Puss Puss an old cat, came to sat goodbye to me whilst I was watching TV then 1 hour later found him dead in the linen basket. Now I have two cats one is 14 and other 17, the eldest one is very doddery, Im dreading the day. I have given all my pets the best I can, it is all you can do. It is OK to be sad, your cat will now be with my pets in the great cat and dog paradise.