Just bought a UNI-T UT526 insulation/continuity/RCD tester, from an ebay supplier - =A379 plus =A38 delivery.
First impressions - very positive.
Slight negative - the RCD test lead (3 of 4mm plugs, to mains plug) comes with a foreign moulded-on mains plug, and a UK adapter. OK - I can soon cut that off and fit a UK plug directly.
Quality of all the test leads, quite reasonable. Silicon-rubber cables, shielded 4mm plugs - all generally well-made and look and feel like the safety factor is there.
Manual - fairly basic - goes through all common operations, but not much more. Reasonably good English.
Unit itself, has a bright-red, clip-on plastic cover to go over the screen and all the controls for protection (or clips on the back for storage). Comes with batteries (6 of AA). Battery compartment door is screw-closure, and does this by threading directly into the plastic body. All test buttons and rotary control feel solid and positive. No backlight on LCD screen, but clear and with well laid out symbols. All plugs and sockets go together with a firm push fit, and correctly designed to avoid exposure to conductive parts.
What can it do?
Measure low-ohm continuity (by applying it's own low voltage). Measure insulation resistance (by applying it's own 250/500/1000V) Measure RCD trip times (at various trip currents) Measure voltage (autoranging - but this is kind of a "bonus" feature)
So far, I've tested out all but the RCD trip time - but haven't yet compared it against a known, calibrated tester.
General pattern of use is - insert test leads (different combinations of the 4 sockets used for RCD test, continuity/insulation, and voltage measurement), set rotary dial to desired test, press click buttons to modify test, then press the latching test button to begin the test, press it again to stop - last value (not peak value) held on the display.
All-in-all comes across as well thought out, not a thrown-together design.
Given how much the big-name multifunction testers cost, I'm pleased with this unit. Insulation and continuity being the main things I'll use if for. It's a lesser beast than the proper pro models, at far less of a price.