Well I'm sure you realise that as soon as your partner contributes to your mortgage or bills, then this gives him the right to claim a stake in your property. So if you split up, things could get nasty.
Maybe accept money from him, in the way of a "rent". Most people pay about a third of their salary towards living expenses, like bills, rent or mortgage. So if his monthly salary is �2000, maybe he could deposit �600 to your account every month.
You can then decide between you how much you each pay towards your weekly food shopping and social expenses.