Thanks for all the responses guys.
@Nick G UPS has already sent me the amount owed for import duties £200+ but I expect this will be higher as they charge £13 a day by the time it finally gets processed. I think you're right with regards to the address and UKARA not matching potentially being part of the problem. My thinking at the time was if it was sent to my work address (That imports 100s of Airsoft RIFs and parts every month) it would be less of an issue and also with the item being a RIF not left outside at home or at a collection point whilst I was at work, a more responsible decision. I have contacted the courier but as of yet had little help from them, will try again on Monday.
@Pseudotectonic Attached is the form I was sent along with a RIF declaration (which was easy enough to fill in).
@Asomodai @C-Diddy fingers crossed then otherwise this will have been a very expensive lesson. I did ask the sender to include in the package my home address (image from an invoice from my place of work) alongside my UKARA and image of my Passport but they would have to open it to get that I guess.
@Tommikka well hopefully they are just busy and just haven't gotten round to sorting it but I believe as pointed out the UKARA address mismatch is probably the problem. I'm just stressing abit as it was quite an expensive purchase and worried it will get destroyed.
Thanks for all your help everyone, hopefully I can get it resolved this week coming.