Money problem

Ok so me and my boyfriend are moving into a new house which is £1000 for the security deposit and first months rent

I’m paying £450 of with the money I get back from the security deposit of our current house and he expects me to pay an extra £400 for rent like I normally do

So in total I’ll be paying £850 and he’ll be paying £150

Bearing in mind he’s sat on a lot of savings and I have no savings as I used them for our current house

Am I being unreasonable telling him he needs to pay more?