sorry for being thick but i am sue someone can offer me some advice.

i have a bay window which has half round pvc gutter with two angled returns and a down pipe. the anles need replacing as they are leaking. on going to b&q and purchasing 112mm size angle i thought this would be ok. the angles will not fit the gutter, there is only a small differance of around 4mm ish the gutter is slightly larger than the angle size. i dont really want to replace the whole lot. the markings on my anle are 100 x 135. has thier been any standardisation in past few years maybe.

many thanks in anticipation.