Definitely go see a few other dentists to see what course of work they'd do. If you want braces, go see an orthodontist and see if they think it's feasible to move the teeth in the way you want. With regards to the fillings, you can get them replaced with white ones.
I had a brace when I was 12 and it wasn't removed until I was 15. By my mid-twenties my teeth has already returned to their former state. Additionally I'd knocked out a tooth on the left side, and broken one which had to be removed due to an abscess.
By my early thirties I started to feel very very self conscious about my teeth. I don't think my friends (or boyfriends) ever noticed how I felt or made any negative comments but I hated opening my mouth. I decided that when I had the funds I'd get them fixed and planned on getting a brace and implants to replace the missing two teeth.
I saw several orthodontists but decided I didn't want to go through all that again. I think the fact that I've never liked the shape of my teeth was clincher and they actually thought that opting for veneers would be better.
So, last Autumn I found a lovely dentist and took the plunge - 6 veneers on my front upper teeth. Sadly dental implants weren't an option in the end because I'd been toothless for over five years, and my dentist was worried that my bone wouldn't be strong enough. Instead we opted for two bridges, one of which was cantilevered and held in place by two crowns.
I had the veneer part of the treatment done first. After my teeth we filed down I had an acrylic temporary for a fortnight, and then the veneers were fitted. Because the porcelain is actually transparent, I opted for a slightly whiter cement than the acrylic temporaries. My veneers look totally natural and not fake in the least, I think because I didn't opt for bright white teeth.
The bridges went in a month later as we decided it was best to give my mouth a little break. In order to prepare the teeth for bridges, many many impressions needed to be taken, far more so than the veneers. After the teeth that we're going to take the crowns were prepared and given temporaries, I had to wait a fortnight for the lab to make the two bridges. During the fitting only one bridges fitted perfectly and my dentist wasn't happy with the second so he decided to get it remade (at no extra cost). A fortnight later it was fitted and I was finished in time for Christmas.
The total work cost me a little under £10,000 and I can honestly say it's the best money I've ever spent and wouldn't hesitate to encourage anyone to have cosmetic dental work.
However.
Having been through the process, it's both invasive and painful/uncomfortable. I originally looked into getting the work done abroad as I know it's cheaper and the standard is just as good. I was quoted a little under £3000 but that was for what I thought I needed doing, and not what I ended up getting done.
In the end I decided against it just incase something went wrong or I needed to go see the dentist between sessions due to discomfort. In my case I definitely made the right decision to stay here as my temporaries needed a slight adjustment and one of the bridges had to be remade. If I'd have opted for the work to be done abroad I would have spent more time (and money) on flights than I'd have expected.
So, in short, do your homework throughly before committing to ant course of work. It's also important you like the dentist who will be doing the work and feel he understands what you want, and listens. For me, the fact your dentist is trying to up-sell you a lot of crowns is a red flag for me, and if I was in your position, I'd definitely see a few more people.
GOod luck OP with whatever course of action you do decide to go for. And if you do have any acrylic temporaries, be sure to stock up on Bonjela and do not eat anything spicy or brightly coloured for the entire time they're in place. If you do, you will end up with orange teeth!! (Thankfully I knew to stick to beige and white food thanks to a friend who ate a curry when she had a temporary tooth and it turned bright orange! She was stuck like that for a month until her porcelain crown was fitted!!)
VERY LONG POST - SORRY 