Hmmn. I don't think you would have any claim, being unmarried, on his home anyway, unless you contributed directly to the mortgage repayments (if any) or deposit - in which case you would be entitled pro rata to have back what you put in.
Therefore I can't see any point in the cohabitation agreement, other than to be able to say at a later stage if you split up "nah nah, told you so, you're not entitled to anything".
A cohabitation agreement will have cost him quite a bit to draw up. One wonders why he didn't just draw up his will to favour his own family, if thats what he wants. Or to put it into a deed of trust.
The law would award you financial provision if you were married to him and got divorced, so I would be suspicious that he is trying to have the benefits of a relationship with none of the risks.
The law would benefit you on divorce because the law recognises the contribution of the non-entitled spouse, financially and in other ways. In other words, it is not unreasonable to expect to be compensated for giving up your time and effort, as well as the possibility of establishing your own household or getting joint ownership of a house with a more generous man.
I am therefore left thinking that this relationship is a big risk for you, in terms of your future security, and that your DP doesn't care one iota about your future security. I also think any concerns he has are misplaced, since you own your own place already (and therefore can hardly be mistaken for a scrounger) and he benefitted from living in it while his own house was being done up - a benefit that his newly drawn up agreement ignores.
I don't like the sound of this and personally wouldn't accept it, as I place my future security ahead of a relationship.