Yes, you could probably do it yourself. But by the time you've sorted things out, worked out what to put where and found out how the HMRC "instant confusion" website works, wouldn't it be easier to ask us? After all, if you spent the same amount of time doing what you're good at, you'd make far more than we would ask for in fees.
HMRC will tell you "tax doesn't have to be taxing". Yet they make the whole process a nightmare: it's as confusing as it could be and littered with pitfalls. Fall into one of their traps and it could cost you big-time.