Is ericaceous compost ok for non-acid needing plants?

[MurielTheActor]

In a total fit of combined absentmindedness and sheer laziness I filled up a (big heavy) pot that had a dying rhododendron in it (there was about 4ins of old soil in bottom) topped it up with new compost (so it's about one quarter old and three quarters fresh) and planted a climbing hydrangea.
Will this do it any harm?
Or will I have to unpot, tip out the old compost, refill etc it really is a very heavy pot...)
(the guilt, the worry, anyone would think it was a child...)