I just moved to the states from the UK basically the opposite of what you did.
You cannot own a gun in the UK unless you have a firearms certificate for firearms and shotgun certificate for shotguns. To get them you have to be at least a permanent resident I think (unsure on that ) you have to have a letter from your GP in the UK. You must have reasons to own guns in the UK mainly target shooting / hunting. Going clay shooting is a good reason to own section 2 shotguns. That’s is any shotgun that has maximum capacity of 2+1. Anything more than that you need a fire arms certificate. Again with fire arms certificate you must be a home office approved shooting club member. That is a reason to apply for firearms certificate. But that will be just for target shooting you cannot hunt with them. So if you want hunting then you must have a land with permission from the owner and that land must be suitable for the caliber yoi applying for. Or paid stalking is another reason if you can’t find any land permissions.There is NO public land hunting in the UK.For both FAC and SGC you must have a proper gun safe attached to a concrete wall or floor. Once you apply for either or both with valid reason you have to wait a long time with most of the forces nowadays. An officer will come and interview you check your safety measures and your reasons. Then as I said you must get a form from your GP( doctor ) regarding your mental Health and stuff.
Your handguns are a no go. Remember self defence is not a valid reason to own any guns in the Uk. There is no 2nd amendment there.suppressors are called moderators in the UK and they must be applied just like ti apply for a rifle. Again you have to have reasons to own every caliber you asking for. marrying someone will not get you any special privileges. Bringing guns back to the US is pretty simple. I just took 10 guns with me. My best advice would be leave your guns in the states and once yoi settle in the UK apply for fac and sgc and buy guns there. And if you decide to move back you can bring them guns to the states with you when you move as your personal property. Get ATF form 6 approved. I’m sure there are other members who are here with more knowledge than me.
You can donate your guns in the US to me


. God bless the second amendment. I moved here last year and bought 5 hand guns and an AR