Question Htc one regional settings

Hello, guys I have experience with flashing android devices but with the new devices everything is more complicated. I bought a phone but is designed for ASIA region. I live in UK, in internal memory has some applications in chinese language and I decided to download european firmware. Here the problems come. First I need to change CID which required S-OFF. This took me a lot of time because I'm with 1.57 HBOOT. Root and custom rom as well. I also changed MID. I'm not sure why because nothing happend after this changes. I still can't install Stock European ROM. Sometimes, receiving error 155 or stuck at checking header (5 %). Is my goal possible at all ?