First, let me get "rent" out of the way.
There is 100% nothing wrong with renting. A lot of people will tell you you are just throwing your money down a hole and you will never get it back, but the sheer honest truth (IMO) is that you are paying for a service. That service includes repairs, a place to live, and the flexibility to change your circumstances if you need to (have a kid, get married, kid goes off to school, etc etc.). With a house purchase, it takes a LONG TIME to get to a place where the money you are throwing into that "investment" gives you any kind of return, AND that return is highly dependent on things that may not be in your control (housing prices, exchange rates, current neighbors, all kinds of fun things).
That is not to say that buying is flat out bad, but don't discourage renting as a tool. No matter what some people say, renting is a perfectly reasonable thing to do, and actually a good "investment" in many, many, situations (i.e. you lose less money than a purchase).
I went through all that, because there are people that will tell you to "always" buy. These people are wrong. Look at their past history and you will often see, one foreclosure, or many house purchases. Just keep in mind that it takes a long time to get "positive" on a house purchase, and in some cases you may never get positive.
Buying in a city
Purchasing a house in a city is a gamble. That area may improve over time, or it may fall into a "bad neighborhood" over time. Yes that LAND is a good purchase, it will probably go up in value in the big picture, but that could easily take 50 to 100 years, maybe even longer. Also unlike a "house in the country" you are usually going to have stricter code enforcement, AND more codes/laws to follow. For no other reason than there are more people around. Make sure you understand that before going in.
Buying in another country
Buying a house in another country may have some serious legal issues, but we will ignore that for now as requested. What is more likely to impact you are "social" issues. A made up example (sorry, don't buy houses in London) would be the kitchen. In the US it is often common for a house to be sold with no appliances in the kitchen. Is that true in London? When you go to sell the house would you be expected to furnish it first? Again a made up example, but you should be aware of this. Also, there may be subtle ways to tell the "direction" a neighborhood is heading in. I know those ways in Florida. Do you know them in London?
Now for the money.
So, the rule I like to follow is that up to 1/3 of your gross income should go towards "housing". Now that's important to know that "housing" includes rent or mortgage AND any services (landscaping) you must spend to keep the house, including repairs and setting aside the "roof fund".
You make 2,500 a month (I know you said net but it's the number I have to work with). So I would suggest a mortgage no more then 750-800. Then pest control (depends on area, here in Florida you NEED it), and lawn care service (depends on lawn, a real nice to have sometimes) should come in under $100. So you are spending $850 to $900 a month on "housing" and the rest of whatever the gross is can go to the "roof fund". The roof fund is important. Your Heat/AC will break, your roof will need repairs. This is part of the ownership. But that fund should not have to grow very fast. Even if it's just $20 a month, by the time your roof needs repairs you will have a nice "nest egg" to work from.
Of course if you don't need pest control, or can handle that yourself, or if you don't need lawn service, or you do need some other service, then those numbers should be figured into (or out of) your "housing costs". Insurance is certainly part of the "houses costs" line item.
A note on renting
The number for renting is the same. 33% of your gross income for rent + renters insurance + any other required services. It's a lot easier to get out of a lease though. If you have to break the 33% rule, then renting is the way to do it.
A note on sentiment
There is no other viable reason to buy a house as a normal individual. If you're an investor, that's a different story, but as a normal person, the only real reason to buy a house is because you like it.
One last thing
I am a strong believer in the concept of "Don't buy stuff you can't afford"! 33% is a good number and it leaves lots of left over money for things like investing, savings, retirement, and buying furniture for your new house. That been said, you may notice that with a 2.5k income your housing costs should not exceed $825 (again that should be based on your gross not net). Yep, that's a small number for a big city. But perhaps you should consider the fact that you can't afford to live in that city. What about the outskirts and commuting? How about a new job that pays more, or a job that is in an area where the cost of living is less? In my experience it would be much better to restructure your entire life to hit that 33% than to "force it" by having housing costs at 45%. There are ways to get that housing cost down, or the gross income up (like a room mate, or renting a room in the house if you can), and they each have their own risks and should not be ignored. But that 33% magic number really is a good place to sit. (But don't go changing you life because it's 34%, you have to use common sense).
