It will not be very difficult for Real Madrid to get Bellingham if they wish to get him. It is not always a problem for Madrid to get any player they want before they have the money and again they cannot be seen as the biggest club in Europe which every player will like to play in for prestige and fame. Bellingham himself will be happy to play on the big stage of Madrid.
I am not so sure if Real Madrid really is the most desired club for Jude Bellingham. Yes Real has won the Champions League last year which was a really great achievement, but we also have to admit that they had a huge amount of luck to win that title. They were the weaker team in all 3 match-ups against Paris, Chelsea and also against Manchester City but they always managed to go through with very late goals.
So even though Real is probably the club with the biggest and most glorious history i don't think that it is the best club at the moment. I think ManCity, Liverpool and FC Bayern are stronger at the moment for example. Also Bellingham is english so i can imagine that he wants to play for an english club.