I'm a bit late to the party here but do have a long running love hate relationship with MDF. Love it because its cheap, hate it because its cheap! lol

As others have said, the furring is because B&Q supply cardboard badged up as MDF - yes its really that bad. Complete junk and I'd avoid it at all costs, I've never got a decent edge finish from this stuff yet.

Medite is ok at the budget end though thickness's above 25mm do have a rather mushy core and again you'll get some furring but nothing like as bad as B&Q rubbish. At the top end you have Valchromat and I love this stuff. Zero furring, retains very small details and can be sanded smooth - almost like plastic when sanded upto 1200 grit. Its expensive though at £80 for 25mm thick 8x4ft sheet.

For reference I mostly cut at 7m/min 11,000rpm and 100% cutter diameter for DOC. Use carbide tooling and you can get amazing tool life, not sure how long exactly but a few months of use almost day in day out for me in MDF. Key to increasing tool life is keep your rpm low and your feedrates high.