If you pack it extremely well, then standard parcels might be fine. Or 1st class recorded might be better for slightly faster delivery, and you can make sure it got there on time.
Packing it shouldn't be too hard. Wrap it in some bubble wrap. Put it in a box full of polystyrene. That should be OK.
Royal Mail treat parcels like sh*t from what I've heard, but I think most stuff arrives OK. I had a 1438 monitor sent via standard parcels and it arrived fine.
If you want to give your A4000 allthe care it deserves, then send it via special delivery. But that will be much more expensive.
Standard parcels would be about £10 - £20 I'd think.