Hi mate
Have a look at the pulleys to see if any of them are shiny/glazed, if so take the belt off and clean the pulley(s) with emery paper to take the glaze away, when you’re at it check the belt for any wear/burn marks too (there shouldn't be if you have replaced the belt). Over tightening or leaving it too slack, the belt could cause the squealing noise too. Find the longest point (pulley to pulley) and make sure you can only get about half an inch give on it (twist it). Check the pulleys to see if they are all straight/aligned as that could cause the noise too if the pulley’s are offset. That's all I can really think of just now other than the timing belt, hope you manage to get it sorted buddy!
