Have placed three orders with Hannants since last year--the most recent on 16 Oct. First came very quickly. Second order took weeks. The word was that US authorities were checking packages coming into the US by airmail between Nov last year and Jan this year, and created a huge backlog. The order did eventually arrive. You may be experiencing the same thing. Normallly they do ship the next day, but after the package gets into the hands of the postal service, and has to pass through security, it can get delayed.
I also emailed them once at the time, but also received no reply, so there seems to be something lacking there in customer response.
At the time (Nov 10 to Jan 11), there was another UK hobby shop (Model Hobbies) that actually suspended shipping to the US while the increased security measures were in effect.
I expect you'll get your order, and I hope to get mine, but it may take awhile if US authorities have some more stringent procedures in effect.