I've not used them, but my brother has used them for my nephew because he has a tendancy to kick off the covers and wake himself and them up. I think you just need to be a bit careful about the tog rating. I know a few people who were looking for them for summer babies (not a problem you're going to have!) and they couldn't get a low enough tog.
Will have tolook up the recommended tog - Do you know Tilly? Tilly what do you do underneath ... sleepsuit?
We had them for Charlotte up til about 10 months, I used to put her in a vest and sleep suit in winter and then in summer I managed to find a low tog, and we just had a sleepsuit on with the grobag. I think you'll find what is best for you Wobbles depending on how warm your house is etc!
The tog depends on your room temperature. We go for the 1 tog when it's high summer (as suggested) and 2.5 for the rest of the year. They recommend a vest sometimes if it's very hot, but we always put Bethanie in a sleepsuit or sleepsuit without feet (not sure of their name) as her arms get really freezing. Heres a good guide from the Grobag site: https://www.gro-group.co.uk/grobag/sizes-togs-and-what-to-wear/ By the way I just wanted to add - they do give you guidelines on what your baby should wear, but use it as a rough guide (im not saying to put your baby in a 2.5 tog bag, in a vest and sleepsuit in a 26o nursery, just don't follow it exactly). We did at first, I would constantly panic she would overheat or be too cold and was worried to put an extra layer on just in case lol.
Grobags are the best! Charlie won't wear one now, so he wakes up when he's kicked his sheets off. During the winter, we put Charlie in a vest and sleepsuit under his grobag, but in the summer, we just put him in a long-sleeve vest. They're quite hard to find, so I used to stock up on different size long-sleeve vests when I saw any. I found some great things in Tesco's a couple of months ago - they were long sleeved with poppers down the front like babygrows, but had the bottoms like a grobag. But they were made of the same material as a babygrow. So, basically, a babygrow with sleeping bag shape. Great for the hot weather.
Olivia still wears a grobag at 19 months, I think they're great. Originally I bought a "Grobag" one from John Lewis for £25.00 but then I kept seeing "sleep sacs" in supermarkets and other shops for around £12. I've been buying these ones as I can't fault the quality and do the same job, just half the price.
