Very popular British records to come online

The National Archives (TNA) have announced their intention to close their operations at the Family Records Centre, located in Myddelton Street, Islington. in 2008. Services will be moved to Kew in southwest London at TNA's main location. The Family Record Centre's recent newsletter explains the rationale as economic, coupled with a greater online availability of the service they offer.

Buried in the newsletter is the sentence "Meanwhile we plan to make other records on microfilm, such as RG 4 and PROB 6, which are very popular at the FRC, available online within the next couple of years." New records online are always of interest, but what are RG 4 and PROB 6?

RG 4 is General Register Office: Registers of Births, Marriages and Deaths surrendered to the Non-parochial Registers Commissions of 1837 and 1857. Find details here.

PROB 6 is Prerogative Court of Canterbury and Related Probate Jurisdictions: Administration Act Books, 1559-1858. Details here.

Although I've not used them these look like useful records to have online.