You and your girlfriend have been seeing each other for years and she wants to move to the next level, whether it is moving in together or walking down the aisle to say I do, she wants something more than what you are currently giving her. You may be thinking to yourself things are going great or don't try to fix it if it ain't broke, but remember you are not the only person in the relationship and you owe it to your girlfriend to tell her whether or not one day you really will take the next step or if you are just having her along for the ride.
Don't consider whether or not you are hurting her feelings by telling her the truth because if you don't tell her the truth you are hurting her more than you know. If you are not into getting married or moving in with her you are holding her back from the dreams and hopes that she has of living happily ever after with her white picket fence. Be brutally honest so at least shell know what to expect, just don't expect her to sit around waiting until you are good and ready to marry her. Give her the opportunity to decide whether or not she wants to stay in the relationship or move on with her life.
Once you have gotten into a relationship with a woman, even a London escort, eventually she will want to move to the next level in order for her to feel as though the relationship is moving somewhere instead of remaining stagnant. If you are one of those men that could never see himself tied down in a relationship, you need to let her know very early on in the relationship so she can decide whether or not she wants to stay. That's the least you can do.
If on the other hand you are just afraid and you don't know why, you can seek professional help or question yourself as to why you feel so threatened by taking it to the next level. Try to figure out if there was a time in your life that had obstructed your vision in this area but whatever you do, you will need to get help or the woman that you love will walk through the door forever without looking back.
Being honest in any relationship is the key, even with a London escort, whether the person accepts what is being said or not it helps to clear the air and both people will now have the same information. What they do with the information is a whole other story by itself.