I think the newspaper announcement has a misprint (or you have misread it). There is no "Old Chorlton" in Kent. Based on the district in which the marriage was registered I am confident that the church in question was St Luke, Old Charlton. Most of the registers in this part of Kent (now south east London) are held at the London Metropolitan Archives and are therefore available via Ancestry. St Luke's are not - they are at the Greenwich Heritage Centre.
You have two choices: either contact the Greenwich Heritage Centre and see how much they will charge you to find the relevant entry and photocopy it for you, or order the marriage certificate (which will be identical to the entry in the register) from the GRO using the reference you have already been given. The latter route, if done directly, will cost £9.25 including worldwide postage.
Hope this helps