Collect+ might be of interest to you. I sent a massive parcel with them (from Suffolk to Sheffield) just before Christmas, with no problems. Parcelforce would have charged me £16.40 to deliver that parcel. Collect+ charged £8.29.
To use their service you simply pay for your parcel label online, print it out, attach it to your package and drop it off at your nearest collection point (which, for me, is a local Co-op shop). I've entered several friend's postcodes (all across the country) into the Collect+ website and everyone of them seems to be within about a 5 minute walk of a collection point, so there's very good chance that you'll be near to one too.
The online tracking system is a lot better than Royal Mail's (which usually tells you little more than 'it's somewhere in the system'). You can see exactly when the package was accepted at the collection point, when it was collected from there, when it was processed at the local sorting depot (and again at the central processing point), when it was put onto the van in the delivery area and when it was delivered to the recipient.
I'll certainly use Collect+ again:
http://www.collectplus.co.uk/