It depends upon your expenses - e.g. living in London, buying a house, paying overseas university fees, etc, is expensive. For me, decent would vary from £100k (no mortgage, cheap area) to £300+k (expensive area, e.g. London, Silicon Valley) PA.
A realistic starting salary in computing (outside London) is ~£35k for a top graduate. A career peak salary (outside London) is ~£150k, for someone very good.