Sektor

That is correct, the 30 quid are already in the pot - 30 € + 75 € = 105 €. We calculate the odds we are getting as follows: € amount we need to call / € already in the pot.

Pot odds are defined as follows:
x / (x + y)
x = $ we need to call
y = pot before our call
So, it is not supposed to be 30 / 135.