New sites often do drop in rank
Sadly the chances are that Google is repositioning to where it believes you should be, most often new sites and pages get temporary boosts to allow them to catch on so to speak. I've seen what your experiencing hundreds of times and can assure you what your seeing is most likely out of your control until your site becomes more established (trusted) by Google.
Having Correct Metas, Title, Canonical doesn't mean your necessary rank straight away, which in your case you have but now its re-adjusting you.
Looking at your front page only and not going any further I can see that the title can be improved since it's too long and your diluting your keywords. Personally I aim for 60-69 characters but it can be longer Google uses pixels in width on the title so depending on the screen size if they have large screens it'll display most if not cut. 60-69 Characters works on ipads and that's generally what I use.
Currently your using the title tag:
The Bakery Box - Catering - Quality Homemade Produce, Ayrshire - Baking, Buffet Selection, Hot Dishes, 3 Course Meals and Tray Bakes
It's too long and will be chop and it looks a bit spammy. If you want your site to rank for lots and lots of things then break this down by making a additional pages. Pages that try to rank for far to much are diluted and hardly ever work unless you have a Good adword campaign and content that people will link too. I'd opt to use something like:
The Bakery Box - Catering Quality Home Produce in Ayrshire since 1958
Meta Descriptions and Titles should be unique
Also every page should have a unique title and meta description, if you don't then your not describing your pages very well and Google will adjust your rankings even more, I suggest you make your titles and meta descriptions unique and make the metas desc no longer than 157 characters. Check this little serps emulator out.
I noticed that you have Menus for some of your dishes, you should get some rich snippets on their so they are displayed in the right format. Check out Googles Rich Snippets.
Lots of text content is Great! But Text and Images is even GREATER!
I noticed that a lot of the deeper pages have a lot of text with not a lot of images, Google loves rewarding sites that offer a good experience and imagine by only having text your limiting your experience you offer. Try to use more images on the deeper pages, Having a nice front page is important but the inner pages should not go ignored, in fact I find it easier to rank my inner pages on all of my sites than I do the front page. Also images include things such as alt tags which can strength your authority in your niche.
Try to read more sites
From what I can see looking at your site is that it could do with some more SEO work but with this said you are on the right track and the fact your asking on here is a great start but webmasters stack as helpful as a lot of people are on here won't be able to provide you all the advice you need in one single post and you can see from what I've wrote its already dragging on already. I suggest you look at as many sites as you can and learn the ins and outs. Avoid anything black hat as much as its tempting to get quick results its not worth it and it'll only come back and slap you in the face where it hurts...
A few useful sites
- Local Rankings - Answer by Me
- Matt Cutts
- Seomoz - Beginners Guide to SEO
- Search Engine Land SEO Guide
Once your on Page SEO is done, then its all off Page SEO
Once you have these elements fixed its all down to off page SEO, since your business is in Ayrshire you want to work on your local rankings which will also help your national rankings as well. There are many guides on the net how to get better local rankings so I won't bore you too much, oh also there is a lot on here too (Local Citations).