That sounds like luck tbh, I had a quick flick through their site and couldn't see them saying they pre-pay import VAT for the UK (unless it's really buried in some document I couldn't find). I've used them many times and one occasion was only a few months back; I might've gotten lucky once or twice long ago but mostly I've paid import VAT and fees etc. As with any import the chances of that and associated cost all varies by the time of year, courier used, paperwork, who at customs gets your package and how much they care if they do in fact decide to open or do anything with it at all. Obviously it should always be the same every time legally speaking, but that's been my experience having imported stuff a few times a year for longer than I want to admit ?
Personally I've switched to mostly getting RIFs in the UK, where possible anyway (if it's not here and I still want it then I'll happily import). Varies case by case of course but it's usually worked out to be right around the same price or sometimes cheaper here. Right now I want an ICS DD Mk18 and the 2 best prices I've found are WGC or F-S:
https://www.fire-support.co.uk/product/ics-dd-mk18-s3-black-airsoft-gun-aeg
https://www.wgcshop.com/products/ics-180s3-1
After shipping and the likely VAT the F-S route is a good deal cheaper, will get here a lot quicker with less chance of loss or damage, better warranty practicalities and no chance of kevin the world's coolest man at customs ringing you up to have an argument because he doesn't know the VCRA.