The first thing that's important to understand about aSIM only contracts is that not having a mobile phone means that your contract is much cheaper but also that it carries much less risk to the network.
A mobile phone is a pretty expensive product so when a mobile networks gives a customer on they want to know they will be paid for it - which is why they credit check all customers and reject anyone they think cannot afford the phone.
By taking the mobile phone out of the contract the cost to the network is much lower and so they are willing to give more customers a contract. Although some networks do check customers on some level (usually that their bank account is correct) the checks are much less restrictive and customers with poor credit are much more likely to be accepted for even an Unlimited Data contract.
Simsave.co.uk welcomes all customers and we love finding customers who have been rejected elsewhere a contract. We have a huge range of data allowances for every budget and even if you just want a sim for 30 days we have options for you!