Magento Custom Development

We are using Magento 1.7 with a standard onepage checkout.

Two jobs required:

1, We would like to make telephone field, on the checkout, required for every country except for the UK. So if a user chooses the UK, they should have the option to complete the telephone field. If a user picks any other country, the telephone field should be required.

2, We need to prevent the input of "+44" being inputted, via the telephone field, into the database. If a user inputs this combination into the the telephone it should instead be replaced, using PHP, with "00" and this number should be stored in the db.

Thanks.