Would you mind me asking which app are you using for UK postcodes and how did you enter the wildcard rules? I tried one app out and the wildcard rules didn't seem to work so I am thinking that I might have done something wrong.
Any advice would be appreciated as it's driving me mad trying to set up shipping for various parts of the UK and Ireland.
I have given up for now as I too nearly threw my computer out of the window! I tried a few different apps but they all seem to be designed for the US and not the UK. I don't think they realise that the UK has different shipping zones such as the Highlands and Islands of Scotland where shipping is a lot more expensive. I have read many threads and everyone in the UK is unhappy at not being able to do such a simple task.
I am now looking at other options as looking back on old threads this issue has been going on for the past 5+ years and Shopify are still no further forward with resolving it!
I used postcode shipping and I had the same problem i.e. channel islands, Isle of wight etc. being classed as different countries. I have sent a screen print of the different zones I created and in each zone are different categories for weight, order value and highlands. I have also taken a screen shot of the wildcards postcodes, which I hope helps.