I have not been road riding long on a Giant Defy 1 2012 which has Tektro TK – R540 brakes fitted. What is there I can do to upgrade them as they never seem like they can stop me down hill . I have been running 203/185 discs on my mtbs so have always been used to good brakes which stop me any where. Is it just brake blocks that need changing or the whole brake set up.

They’re usually pretty good on the Defy’s, have you checked they’re set up properly?
If that hasn’t made any difference, try some different pads before you start spending on new callipers.
FWIW mine are useless on my cx bike, won’t even lock in the mud, but you get used to it.

I have been thinking the same on the same bike, the power is fine but they are a bit wooden. A change to some decent cartridge pads should cure it.

New pads, decent ones at that, and possibly new cables if they’re dragging a bit. Should make all the difference, as usually cheaper road bikes come with rock hard brake pads to last a long time, but not stop you that effectively.

I’ve just gone from a Giant Defy with Sora brakes that weren’t that effective at all, to a Merida Scultura with vastly better brakes and honestly, there’s no shortage of power!