Why can't I download uk apps

Your account is based on the country you registered, independently of where you are at the moment. You can create a new account in the App Store for the UK store, as long as you are able to top it up with either a gift card or a credit card with a UK billing address. I hope it helps.

You do not need a new ID for a different country. You just have to change the account information for the existing ID. The account address and payment method have to be associated with the country you are located.

Yes true, but that applies only if you do have two payment methods (one for each country). In my case there was always only one payment address, but apple chose to force me to a different store by location of my computers IP, Now they changed their mind and im stuck with hundreds of Apps which i cant update anymore.

Ditto. I have moved back and forth between Switzerland and the US and Apple forced me to open up brand new accounts. For some reason they just will NOT let you change your country. The first time I did it without realizing the implications, and when I returned to Europe I sent in a ticket, the reply to which was simple: create a new account, leave the old one without a valid payment method, only for the updates. 😕

additionally, if you change the billing country in iTunes, you can not anymore receive updates to previously purchased Apps.

This is a known issue and there is no fix currently for that.

So what do you enter as payment info in the second account?

It requires me Credit card number from the other country.