Deckerhead,
Have to agree with Lee Enfield on this occasion. These "made up" PH rifles are sometimes very difficult to conclusively identify. Its only a combination of lots of similar identifiable parts that assist us. M85/86/87 & 1200TX's have been chopped and changed so often even the PH engineers haven't got a clue what they are looking at via photos most times.
I am assuming you have spoken to the previous owner as to where he acquired the bits from, to help you, as he may be the one who acquired them?
If it shoots well enjoy it.