Lets start with flowrate for hardware. You've basically got 2 choices, powerheads or a closed loop. Powerheads are cheaper and easy to impliment. Closed loop systems are expensive and complicate to impliment. Powerheads can limit you in the livestock you can keep. Soft bodied inverts like sea hares, anemones, lettuce nudibranchs, etc can get stuck to the inlets of powerheads and perish. Closed loop systems if properly constructed can allow the keeping of these soft bodied inverts. Unless you absoloutely have to keep one or the other of these inverts I'd go with powerheads. On a 70gallon you'd want 1400GPH worth of flow or more prefferably out of two or more powerheads, evenly or uneavenly matched in flowrate. The best powerheads for a large tank BY FAR are Tunze and Seio.
Are you considering a sump at all?
As for lighting, I'd suggest a basic luminaire something like an Arcadia with either 4xT5 lamps or 2xPC lamps spanning the length of the tank. Metal halides would offer you more flexibility for higher light corals but you'll have to make that decision yourself on whether you want to keep them or not.
And for skimmers, I'd suggest something like a Deltec, Aquamedic, Tunze, or TMC skimmer in the UK. Running a skimmer in-sump is always easier but a hang-on can be done.