If that works it's a cool idea, that said there are phones that dual sim WITH an SDcard (as I have one) it just isn't 4G.
It has been done before

If that works it's a cool idea, that said there are phones that dual sim WITH an SDcard (as I have one) it just isn't 4G.
Here is for you guys who like Stock Android.
http://www.gearbest.com/promotion-apollo-lite-special-671.html
It's above your range, but the Moto G 4 has what you need. Might be a while until a second hand one gets down to £100, but if you (they) can stretch to £170, it's a decent device.
Quick question. How can tell if I have a custom ROM from my supplier or official miui 7 (mediatek) so no global ROM for me. That's on the redmi note 3, 3gb ram 32gb storage. Currently showing 7.0.19.0.0(LHNCNCJ). Hasn't updated since I've had it in nearly 3 months. Also tells me there are no updates.
Just saw this thread. A few months ago bought a Xiamoi Redmi note 3 pro. Absolutely outstanding. Basically every bit as good as a galaxy S6 but cost me £130. It even has some features that the known brands don't have like timed power on and off. I will never buy another Japanese/American/Korean phone. These are the future.
Disclaimer... having said that. I do realise these phones infringe many patents and in buying them I am hurting future tech R&D by the companies that developed the technology in the first place. So moral dilema there.
Quick question. How can tell if I have a custom ROM from my supplier or official miui 7 (mediatek) so no global ROM for me. That's on the redmi note 3, 3gb ram 32gb storage. Currently showing 7.0.19.0.0(LHNCNCJ). Hasn't updated since I've had it in nearly 3 months. Also tells me there are no updates.
After installing MIUI, did you clear Dalvik and cache? Also did you use the global ROMS or the Xiaomi.eu ones? Maybe it has something to do with the location set in the device. Also was the device maybe rooted with MIUI (some apps refuse to run then)?
Was going to buy the XIAOMI Redmi Note 3 pro prime today and then saw the Moto G 4th gen (2016). Spec wise it's similar apart from no fingerprint and 2gb of ram. But it's got a faster cpu, clean MM, excellent camera and 800mhz 4G support. Going to look at some more reviews and might just get one from Tesco.