personally think they are terrible. i used them for my online store when first getting started as i was able to drop the items off down my road allowing me to do this in the afternoon whenever suited me and not having to wait around.
started sending 1/2 packages a day at one point with them and they were good cost, however it was when things went wrong i didn't like them. they would often damage my parcels, not tell me or the customer, and then chuck away the parcel as it was classed as perishable goods. crazy couldn't believe that they could damage my items, then chuck them away without telling anyone, and then i'd not be covered for this.
also as far as i understand, collect+ aren't a courier, they then subcontract this, they just arange for it to be dropped off at newsagents and then collected.