Shopping and fashion

With the nice weather back in town I found once more that I have nothing suitable to wear for work. With winter and the coldish weather it was easier to cover a multitude of sins with my old and trusted fleece jumpers but now I truly don't know what to wear.
People here is so much fashion conscious than in England that I'm starting to feel under-dressed. Specially because I've got 3hours teaching to a bunch of the upper-level investor group at the bank and they do wear what I still call "Sunday's best". The guys all wear smart suits and the women look like they stepped out of a make-over fashion mag and I do feel totally out of place there. A bit on the boring side of fashion, you know, conservative, mostly black smart whatever, but always with full make up and high heels.
So far I kept on thinking: Not my style anyway. But as the weather is getting warmer I'm finding that my usual uniform of jeans and t-shirts is not good enough... at least not my old 1-pound t-shirts from Tesco!!!
So I started my own what-not-wear analysis and I'm totally lost. Help!!

It's also a sort of mid-life crisis as well because, for the first time ever, I'm totally loss when I go shopping and I don't even know where to start.
It's not helping that the current fashion here is totally weird. Very 60's, Mary Quant A-line dresses with a twist, no, make that a whirpool. It's like Jackie O on speed. Great if you're pencil thin, which I'm definitely not, and very tall, which, funnily enough, I feel I am as people here is really shorter that in England. One out of two, so far, not that bad!

Under the false pretences that we were practicing vocabulary, I asked my fashionable students where do they buy their clothes, and most of then mentioned Massimo Dutti, Zara, Mango and El corte inglés (the local department store, the Spanish Debenhams). So off I went searching for new stuff.
The clothes at Massimo Dutti were far too boring and in any case, far too expensive for me at the moment. Well... even if I have the money I wouldn't buy there, most clothes were in black and so traditional that not even the Queen will find anything there.
I like Zara despite the fact that its sizes are ridiculously small and nothing seems to fit me.
Anyway, I tried one lovely yellow A-line dress there but I looked like Big Bird! Not good. (click on the link and skroll down until you can see the dress). At least not good for teaching as it will drive my students to distraction. It doesn't help that I'm shopping alone so I don't have anyone to stop me even thinking of try such horrors.
I thought that Mango will be more suitable for me because it's a bit like The Gap, practical stuff, at least on their window. Not inside! They have more or less the same wacky fashion than the other shops. You know, when some style is in fashion all the shops sell the same stuff over and over.
Finally and out of desperation I drove myself to the nearest shopping centre and spend a whole morning there trying almost everything and with the total conviction that I was to buy a few whatever, enough to last me until the real summer heat arrives.
To make a long and tiring story short... I bough a white short sleeved shirt in C&A. One pair of high heel espadrilles (extremely comfortable). And one pair of sand coloured Capri pants.
Nothing to write home about but I'm very pleased because for once I didn't really worried about expending money on me.

Then, the very next day, I went back and bough a lovely withe dress at Mango. It's very plain and confortable and the idea is to wear it with a coloured (Tesco's) t-shirt underneath. I'll try to get a picture here asap.
Of course, now I started to regret that as I'm never totally conformtable wearing a dress or a skirt. But I'm determined that I'm going to wear it, just out of sheer hartheadness: I want to be fashionable!

Any ideas and/or suggestions are most welcome.