i honestly feel i have no say with the flats as they are his properties prior to marriage. So i find it difficult to stand my ground.
Sorry, OP but this is bollocks. They might have been 'his' flats before marriage but when he chose to marry you those flats, along with everything else he owns, became your properties too. Besides, it doesn't matter what went on before the marriage, what matters is your current reality, which is scrimping and saving to complete your home renovations, watching every penny you spend on food and dressing your child in hand me downs while DH's wealthy friends are sitting pretty in a flat you could be selling to make life easier on yourselves! How can you "have no say" in something that directly affects you and your child?
Ridiculous of your DH to say "what if we didn't have the flats"... the point is you do have them! He's just trying to shut down the conversation, using avoidance tactics and let's face it, it's worked! He's made it so difficult for you to have a sensible, grown up conversation about the flats that you've stopped trying and are silently seething instead. But why should you seethe silently? You're "making ends meet" and selling the flats would give you a more comfortable life. You work, you're entitled to be comfortable so why should you struggle?
How dare your DH call you "greedy" for not wanting to live hand to mouth for the convenience and comfort of friends who earn 100k+ and have several of their own properties but still neglected to pay him rent for a whole year! Then they come up with this (frankly, insulting) rent to buy scheme and their son wants to run a business rent free from your other property...but you're the "greedy" one?? Unbelievable.
The fact that you think you're not entitled to a say suggests that this marriage is not an equal partnership.