positivenote - the wall you are talking about is a stud partition wall. These should not be loadbearing, but through time they may naturally take on a bit of the load, and there's always the odd situation where you see a stud partition is actually supporting a load substantially more than it was designed for. Bottom line is, even if you removed this yourself and said 'hey, nothing fell down, looks like its fine', you may be in for further pain down the road as the joists may sag, or you might get stress cracks elsewhere.
This is one area to get someone in the know involved, and be aware that if you need an RSJ it'll probably sit proud of the ceiling surface which will impact that open plan look a little (still worth going open plan though just be aware of this).
Get a structural engineer to have a look for a couple of hundred, and if you get the go ahead, knock it out yourself. If you do need an RSJ then budget around 2k.
I assume the plumber and tiler were looking for 250-300 each per day? Crazy as it sounds this does seem to be the going rate most trades price their labour at. My experience when working with these lads was that only making this rate was 'not making money'...making money is when they get their 300 a day for labour but also manage to conceal further profit in material or sub-contractor expenses - thats why theres lads out there earning crazy cash.
You should get a very decent kitchen from Cash&Carry or Panelling Centre for under 5k and pay another grand or two for a fitter.
No offence to Deirdra but her prices are all excessive, though maybe the gear she was getting was at the high-end, which is where the most profit for both suppliers and fitters is (a tradesman will never be shy about upping the price when he sees the client is spending top whack on the gear as they are less likely to be fussy over price).
Taking Hotpoint as a 'decent' brand DID should sort you out with a disher, washer, fridge, cooker, dryer for 2.5k.
6k for plumbing a bathroom and kitchen is ridiculous, especially in a renovation where all your supplies will be present and its just a case of extending the pipes to where the new appliances will be.
Shop around and source as much materials as you can yourself as you wont be paying the margin the tiler/plumber will stick on top, and you'll be making their prices more transparent (i.e. if he quotes 1200 you know its all for labour).
You can do a lot of the preparation work yourself to reduce the cost: remove existing tiles (can never understand why anyone would pay someone else to do this simple job), pull out existing kitchen etc. - this will reduce labour time for your tradesmen, but also make the job cleaner for them and the price will reflect it (e.g. if its a pain in the ass plenty of lads will charge top whack).
Good luck with the purchase and the renovations - my advice is make sure you have a 15 - 20% contingency fund on top of your original budget to cope with unexpected problems (beware asbestos) and the inevitable increase in your taste as you're out and about viewing kitchens and bathrooms