Hello and welcome. Joey's advice above is great.
I'd just ask do you know which Officer you're going for as there are a few different CRLs, and depending on which you choose will help determine what you need.
No matter what you are getting, Wampa Wear is great and you'll get the tunic, trousers, hat, belt, and potentially gloves from him. The uniform sizing is true to US standards, so if you wear a Medium normally, get the medium. Unlike the flightsuits, the uniforms seem to match up great.
As for accessories, I always recommend, like Joey did, Philoprops for the code cylinders and belt boxes. if you can, spend the few bucks extra and get the real dosimeters he sometimes sells. The sizing on the belt box will be determined by the CRL.
Note when you order the hat, if the disk has a notch or not, again depending on the CRL.
Pick your favorite star wars Officer and get the matching rank bar... make sure to get push button and not the plexi glass (for the higher level submission should you choose to later on).
If you get a blaster, get the holster from Darminsprops on Etsy. He does excellent leather work and I have his e-11 and SE-17R currently, and in the past had a few others of his. Always a perfect fit for the blasters.
Last are the boots. I've purchased pairs from AntiguaHouse and MilitaryclothesUSSR on Etsy. Both are great... just a matter of which have in stock the correct ones... remember, you want the higher riding boot style, not the jack boots as they won't work for the Officers.
Just curious, why would you need the uk garrison clearance if you are part of the scottish garrison?
As for the costume, the classic cheap supplier is cosplaysky but if you want something of a higher quality (but more expensive), there are many other options such as Galactic Costume ( Galactic costumes | Facebook ). Personally, one of my jacket comes from him and it's truly high quality work.
