I bought a 3/8" drive torque wrench off Amazon for doing low torque bolts (it does 10-80Nm) so ideal for timing belt components, brake calliper guide pins , sump plug - that sort of thing. Was only £25 and I've been happy with it. You'll ideally want two torque wrenches to cover all the range of things on the car really (unless you spend big money on Britool or similar). I only have the small one as I'm worried about over-tightening and snapping things than under tightening big bolts.