If you don't leave a will, all of your 'heritable estate' will pass to your husband (unless its value exceeds £473k which, from your question, I assume it doesn't).
If you do leave a will, your heritable estate will go to whomever you choose (which will obviously be your husband in this case). If you've got an endowment mortgage, or a mortgage protection policy, the remaining debt on your mortgage will be paid off in full. If you've not, the debt will move with the house. (i.e. the lender could either allow your husband to take over the existing mortgage or, possibly more likely, issue a new one. Your husband could, of course, choose to pay off the mortgage with any money you've left him, and/or from his existing finances).
The following wording should suffice:
"To my husband [name] if he survives me for the period of thirty days I give free from all taxes and duties payable on or by reference to my death all my interest in the property known as [address of house], or such other freehold or leasehold property as shall be our main residence at that the time of my death".