I bought this CD when it was new, and to be honest the mastering is absolutely dreadful - 'Today's The Day' by the PRO is particularly bad, which is a shame as it's my favourite track. Someone I know who has the original Apollo LPs sent me a rip of this track from the 1970s vinyl, and it sounded SO much better.
Not a reflection on your rip, Cratedigga, which is as good as it can be - it's Apollo Sound's problem, not yours! I've always wanted to re-compile it with decent quality rips from the original vinyl.