As I read it, if that handle came off, it would be eligible for parcel post, insured, at £8.32, delivery up to six weeks:
Pets at home (Who have 2 in stock at my local store) give the dimensions, as follows:
HWD: 44.4x25x23 cms.
Weight: 1.2 kg.

They quote the same for packed and unpacked, which seems odd, it only has to be 24mm smaller (900mm. max H+W+D) about an inch, to qualify, but I can't see Royal Mail waving it through any larger.

If you want me to check it out, the store's just by my daughter's where I am tomorrow and I'm at the Post Office on friday: Let me know?