As with marriage, you still need to make a will after registering your partnership as any will you made beforehand becomes invalid.
You will then be recognised under the intestacy rules, and will benefit from the same exemption from inheritance tax as married couples.
If you have existing wills you can either arrange for them to be amended before you register so they allow for the eventuality of a civil partnership, or you can simply have them amended afterwards.
If you choose not to make a Will, your civil partner will inherit under the rules governing intestate estates, which will take into account children from existing or previous relationships.
You are strongly advised to make a new will AFTER entering into a civil partnership.
If you do NOT make a will your partner will only be automatically entitled to the first £125,000.
If you live together but have NOT entered into a civil partnership you must make a will or your partner will receive NOTHING from your estate.
You can make a single will online for £29.95 or a pair of Mirror Wills for £49.95 here