Looks like I might have bought the wrong mini-PCIe 3G card. I bought a Huawei EM820U but it seems that this is not supported however the EM820W is. Can someone please confirm if it is possible to get the EM820U working or not and if so how so.
For any one interested I did manage to get the Huawei EM820U working.
It was really simple when I realised that this card required a ppp connection and not a DHCP client like the MC7710!
Set ppp-out1 to use USB2, data channel 0, info channel 2 and APN three.co.uk (in my case, for three in the UK)
You will also need to add a NAT rule. chain: srcnat, out interface: ppp-out1 action: masquerade
Use SWI9200M_3.5-Release8-SWI9200X_03.05.24.00, this is what I used an I know this works.
Although RouterOS 5.25+ should work I’d recommend using the latest, 6.12.
If you can not get it to work in the mikrotik then test that it works in a PC/Laptop with a WWAN mini-pcie slot, which I assume you have as you have upgraded the modem’s firmware. You can use AirCard Watcher to use the modem in a PC.