"I've been really looking forward to moving in and making it our home. He has already chosen paint colours, curtains, sofa himself without asking my opinion."
You might see it as 'our home', but he sees it as just his. You are his lodger-with-benefits. He does not see it as your home.
"I said 'is this house going to be entirely your taste then?' a bit tongue in cheek and he said 'yes of course, its my house'. "
See? 'My', not 'our'. My.
"It's upset me as I assumed that if I was living there with him that he would see it as 'our' home, if he saw any kind of a future with me."
He doesn't. Sorry, but he really doesn't.
"We haven't bought together purely because he didn't want to. He is on a high salary and has owned 3 homes previously and thus built up a large deposit over the years whereas being on only 34k a year myself in London it has just never been possible to me to buy on my own. I think he just sees it as he has worked hard to get to this point and doesnt need my contribution (which wouldnt be much) and he would be losing out from buying together...."
Yes, you have it exactly. This is his, he doesn't want to share because he thinks you will split up and he doesn't want to lose half the value to you.
"We met 5 and half years ago and were together for 2 years before he ended things (commitment issues basically). We were apart then for a while but rekindled in September 2017 when he realised what he lost and after a lot of begging and talking and discussions we decided to give things another go, so 'this' relationship together a year and a half."
Begging? That's not healthy. I'm sorry to be so cynical, but in my opinion what he realised he'd lost was regular sex and someone to do the cleaning.
He's showing you who he is. Believe him.
And keep sharing with your sister. Living with him as he plans it to be will grind any self-respect and self-esteem out of you pretty damned quickly, and they are worth a whole damned more than £350/month.