The Monumental Inscriptions for St Luke's are held by the Manchester & Lancashire family History Society. This is stated on the first page of the microfilm that the LDS have. It is a typed Transcription and it does look like the ink has bled.
I haven't seen or come across a plot plan for St Luke's yet.
Cancan 
You could try contacting the mlfhs for a lookup, if you have the names and dates, but I have been told recently that they now make a charge for a lookup, if not a member

Hopefully not

As the mlfhs done the transcriptions in the 1980's/90's? I would think they transcribed all the stones that were there at the time.
The LDS copied parish records that were made available at the time they approached Churches to copy their records. These were mainly done in the 1970's/80's, for the UK

though they are still doing this to date, all over the world. Churches do have the option to state what date they can be copied too. (Many at the time used a 70yr protection date.) So this why many are not available for later dates. It is upto the Church to contact any organisation if they wish to donate anymore records to be copied. (Some that allowed the records to be copied to later date, the LDS have used a cut off date for protection.) (This information about the LDS films and details was told to me by various people who visit LDS genealogical libraries.)
The microfilm for St Luke's via the LDS is not worth spending the money for as it is badly copied. Whether the copy held at the Manchester library is better I'm not sure

Best option is the mlfhs

As previous posters have stated, none of us yet after contacting via persons and organisations cannot find any other records available.
Good Luck with your search!