Unable to activate iBASIS SIM (I Think)

I just received the Thingy 91 this morning. I've inserted the SIM have verified it on the nRF Connect for Cloud.

I cannot proceed to the next step, as the led continues to pulse blue - so I assume not connected to the network.

I am in the UK, South West London (SW15 6BF).

I assume there is no coverage here??

What are my options? If I need a different SIM, what am I looking for?

Thanks