Thank you for replying so quickly
I play the semi slav but after 1. nf3 d5 2 c4 c6 3 e3 white can make black play for his move order with 4 qc2 
i think white has too many anti slavs and want to avoid this by playing a separate system against the reti and english
i think 1 nf3 d5 2 c4 dxc4 is interesting but it doesnt have to transpose into a qga and im not sure if its better than the reti benoni
does black have any other options than these two moves, assuming black plays the slav/semi slav against 1d4

Not for the first time I respectfully disagree with Mr Nieuweboer: I think 2...d4 is a very good choice for Black, as long as you are aslo prepared to play the position after 1.Nf3 d5 2.d4 - i.e. a probable transposition to a Queen's Gambit.

The only reason to play the same way against 1.Nf3/1.c4 as you do against 1.d4 is to avoid theory and with many Black defences, you just can't do it.
The Dutch, QGD and the KID are fine but you can't get a Modern Benoni or a Nimzo - and even a QID is not an option if White plays 1.c4/2.g3.  If you want to play the QGA then 1.c4 is a particular problem.

My choices are either 1...d6!? or a QID set-up against 1.Nf3, and 1...e5(!) against 1.c4 - I believe that White has got to be made to pay for his move order and can't be allowed just to get a d4 opening and cut out all those Black options 'for free'!

No. White has all the chances to get some favourable Benoni position. Why should Black play 2...d4 if he also has
A) 2...c6 aiming for 3.d4 transposing to the Slav;
B) 2...e6 aiming for the QGD;
C) 2...dxc4 which is a sound option?

What do you play against 1.d4 ? You should play a related defence against 1.c4 and 1.Nf3.