The easy way to meet The English Opening, is just copying him. Just play 1. ... c5 and do everything he does symmetrical, until he makes a pawn break.
1. c4

1.c4 d5?! is considered dubious in theory.
Against 1.c4, you should play what you play against 1.d4 since they transpose quite often. There are not very many independent lines in 1.c4 compared to 1.d4 and 1.e4, and many of them equalise easily for black. So as long as you prepare for those lines, then 1.c4 should not be a problem.
If you are comfortable in the positions, you could go ahead and play 1...c5 as in the above post. It ultimately is a matter of preference.

Play 1.c4 e6 then. White is pretty much forced to go with 2.d4 if he wants any hope for an advantage.

Well, I haven't played against 1)c4 in my life but if I were to encounter I would play d5. If 2)cxd5 then i'll recapture with my Queen. Sort of tranposes to Scandinavian/Center Counter which is what I play against 1)e4 :)

It's certainly possible to go e5, Nf6, Nc6 and then d5, which is the reversed Dragon. It's not that easy and you need to know it, since really you're opening the game a tempo down.
The easiest by far is to play your normal opening, then you put the question to white if he is ever going to play d4 or not. The Slav is good indeed, or an atypical KID or even a Dutch. Unlike in the normal lines, you're quite simply threatening to play d5 later so you have the whole centre. Again it's up to white to stop this plan or let it happen.
A ''normal'' development is also totally fine. Again you play e5/Nc6/Nf6 but you're just not going to play d5. It's a closed Sicilian with a tempo down, which is really not that sharp. Common is then Bb4, attacking Nc3. (Look for the Reversed Rossolimo) In these lines you need to know what to do from a strategical point of view since you're not just going to walk all over the centre.
The English opening, 1. c4, is a bit of a problem for me as I sit back and wonder what to do. I usually reply with d5 and gambit via Nf6, but am not sure if this is good or not. Reversed sicilian is possible too but open games are not my strong suit.