Buying a house. Where to start?

Hi there,
I am in salary plus commison career. My basic salary is €25k however my p60 will say I earn €40-50k ++
I am guaranteed my salary every month of roughly €1800(Net). After that my commision could be anything from €500-€1800 extra depending on the month I've had.
I intend to buy on my own at some stage in the next 24 months. The prices of properties I will be looking at will be €180-€210k.
I have no savings to date, and have my car through Finance(€150 per month).
My first question is
a. How much can I borrow? (Is it based on my basic only?)
b. If I'm approved for x amount and I decide on a house thats less than that can I assume that the original approval stands. EG: if I'm told that I can borrow 200k, then I find a house thats 180k, will the bank drop the approval to 92% of 180k.
My second question is
a.The deposit- Where will I get it??? I know I need to start saving. Any ideas on this? Whats the best savings account..etc.etc.
It has been mentioned to me that If I save €7-10k in the credit union I can borrow the rest... Is this advisable??? Or should I just live like a hermit for the next 18months and save the full deposit amount. My family are not in a position to help me with money, nor would I ask them to guarantee anything.
Lastly-Chicken and egg. Should I approach the bank first and enquire about mortgage approval, or should I wait until I have some savings (and a house in mind) and then approach them...
It seems to me that everywhere I look people are buying houses with what seems like very little effort or struggle.. Am I missing something????
Help please... Thanks

Question 1.
a. It depends not only on your income, but your personal situation (married/kids/outgoings etc) would need more info to get you an accurate amount
b. Yes
Question 2.
Save as much as you can - it obviously means you have to borrow less, plus also shows a bank that you have addtional income available to meet repayments.
Many credit unions are about to list with ICB so, this option may not be a good thing to do. How about a gift from a family member? Other forms of security might be usable? Shares/savings/bonds etc