Suit for $600-$800

Hopefully someone smarter than I will come along and lend some better advice, but in the meantime, look at the threads where they review the MTM (made to measure) suit makers like Indochino and Suit Supply. IIRC, Indochino can hit that price point and uses partially canvassed construction (someone else please either confirm or deny this).

If you're wearing something 3 times a week, it's going to get worn faster and require cleaning sooner. I'd stay cheap and go with something that's available.

http://www.jcrew.com/mens_feature/TheLudlowShop/PRDOVR~11707/11707.jsp

I know jcrew isn't the bastion of suiting, but there you go - worsted wool, charcoal and navy, double vented, you can buy two suits for $850 and rotate.

If you do choose to go with a MTM service, get your measurements done properly otherwise you run the risk of throwing money down the drain.

I'm new to this, so take it for what it's worth... but this is the price point I was shopping too.  At a grand or less, honestly, I'd just hit some decent shops and do lots of trying on.  Heck, that's half the fun!  :)  Go with what looks good to YOU, not what the sales associate says.

 

I found a Calvin Klein slim fit suit for less than 4 bills at Macys that I like and fits me well after about $75 or so of tailoring.  Good luck.

I would check out Suitsupply, Massimo Dutti and Zara. I don't think J.Crew have operations in the U.K., but even if they did, I find their suits a bit overpriced. Besides, the Ludlow cut -- linked to earlier -- is far too (wannabe) fashion-forward to work as part of a CBD. The Aldridge cut is better, but only comes with single vents, which is just unpardonable.

I would think since you have to wear it 3 times a week, only one suit would never work.

I agree that 3 times a week is a lot of work for 1 suit.

 

I am trying out Kent Wang MTM in a month or so, you may want to also give that a shot.

If you like slim fit, I would recommend Hugo Boss Red Label or Z Zegna. You can get them within the price range that you desire. They can be quite cheap when they are on sale and most big name stores will offer free alterations for those suits (hence saving you a trip to the tailor). You can also look into Theory which is another brand that makes slim fit suit.

At $800, get a Stile Latino NWT suit on eBay

A little confused. Your location reads as "Oxford", yet you price in dollars. Forget MTM on your budget and with your lack of experience, unless you really struggle to find RTW in your size. Sounds like you need a couple of suits for £550 mark tops. The following are good starting points:
Charles Tyrwhit
TM Lewin
M&S
Suit Supply

You can buy 2 suits from the above (maybe need to spend more for alterations) but expect fused for 2 suits for the total price above. A fused that fits is better than a half-canvassed / full canvassed that doesn't. Also, better to have 2 suits for rotation than 1 suit with a spare pair of trousers, given your intended usage.

If you want to go for the single suit with a spare pair of trousers, add Ede & Ravenscroft to the list (sale £400).

P.s. If you are in Oxford, then check out Bicester. However, from postings on SF, you need to be able to assess what you are buying.

Don't go to Zara, the quality is dreadful.

Don't go to T M Lewin or Charles Tyrwhitt either.  If you can hang on, as was mentioned above, wait for an Ede and Ravenscroft sale.  You can pick up a suit with a second pair of trousers for under £400.  The quality is good at this price point.
 

Head to Bicester village, try to find some polo discount, also try discount Ted baker, I used to wear those to public schools and they fit very nicely.

Sometimes they have some purple label stuff for very cheap.