3 things.....
1) That gun is beyond shit, if you're going for a GBBR avoid AGM. Guessing you're on a low budget, so go for a WE.
2) Valid Defence - UKARA, Re-enactor, Valid/active site membership etc
3) The Price - Gun $180, shipping $84, $264/ £172. Then add on the tax/duty another £40ish, plus the lovely handling fee that Parcelforce/UPS add £13ish. You've spent £225ish. You can pick a new WE up for £260 in the EU.