I used parcel2go for a quote, put in dimensions, etc. and it comes back with parcelforce as the most cost effective solution.

But looking at Parcelforce directly, they specify combined max dimensions length plus girth (= 2 x w x h I assume) 3m.

Anyone had any experience / hassles with them as a result?

use senditnow.com that is parcelforces on line service. abt £12 for a bike. I have had no problems with the stated max size.

Yes senditnow were good, did use parcelforce but were a few minutes late collecting and you had to stick your own label on. Instructions said print off label and the van driver would have one of those clear envelopes, but he just said stick it on! All delvered in less than 24hrs, so would use again.