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I know you say you only want it for defrosting, but if you're anything like me, you will end up using it for so much more - heating up milk for toddler/hot choc, starting off jacket potatoes, warming up plates, to name but a few!
Ours was a little more expensive - around £60/£70 about 8 years ago, but has a digital display, as well as a quick start button, which you just press once & it does 30 seconds. Ours also has an oven function (which may come in handy as the glass in our oven door seems to have come loose ). Have just come back from 4 days with ILs, and found using MIL's microwave rather frustrating, as it only had a dial, not a digital display, so you couldn't heat something for 30 seconds, you just had to guess at somewhere less than 1 minute & even then if you set it for what you thought was 30 seconds it would stop with about 10 seconds left to go IYSWIM.