The English and/or Reti without knowledge of the Queen's Pawn openings
As others said, there are some "pure" English lines that do not transpose into a Queen's Pawn opening. You are never truly forced to play d4.
However, it makes sense in a lot of situations. After all, even if you play in a hypermodern style, you'll still want to contest the centre sooner or later. Thus, never rule out to play d4 at a later move (or you somewhat cripple yourself).
The sweet thing is that you are the one who decides when that d4 thrust will happen. Thus, if you want to avoid specific Black defenses to 1.d4, you can bide your time with 1.c4 or 1.Nf3 and only play d4 later on when they have become infeasible. That way, you don't have to worry about the huge and menacing 1.d4 complex all at once (don't be foolish to think that 1.c4 or 1.Nf3 will completely absolve you of the need to learn theory though!).
Maybe a good idea is to start with a pure English/Reti setup, and add the Queen's Pawn openings to your repertoire over time by regularly analysing in which additional lines d4 might "fit" in your opinion.
The English without knowledge of the Sicilian
The English and the Sicilian may look similar, but their character differs quite a bit (in most lines, anyway). For starters, if Black choses any other answer to 1. c4 but 1...e5 (like 1...c5, 1...Nf6 etc.), and that probably occurs in the majority of games, you are in completely un-Sicilian territory already.
Even if 1. c4 e5 does happen, you don't really need specific knowledge from the Sicilian. Sure, the pawn structures may tend to look the same, but still the way both colours play around them will often differ a lot! In general, while the Sicilian is sharp and tactical, the English tends to be more quiet and positional. For example, it is very common in the Sicilian that the players castle on opposite sides and White starts attacking Black's kingside with his pawns. That sort of thing does not happen nearly quite as often in the English.
In my opinion, learning 1.c4 e5 does not require you to learn 1.e4 c5 (and vice versa). It's nice to combine them (I do), but by no means necessary.