THE DOCUMENTS YOU NEED

Offer accepted! Yay! Now you need to move fast: first of all instruct a solicitor.
To avoid any delay, send him and to your lender the following documents:

1. Proof of your ID
This means a copy of your passport, but remember that has to be certified. You can get your passport certified at any post office: bring there both the original document and its copy, and then fill the ID Checking Service Form.

2. Evidence of your earnings
This means your paychecks and P60. The P60 is an official document released by your company (before May 31) that shows the tax you’ve paid in the last tax year.
In case you are self employed you'll be asked to show copies of invoices, your business bank account statements and your tax return. They accept official digital files.

3. Proof of your address
Any official letter addressed to you and issued within the last 3 months. It can be for example an HMR&C notification letter, a local authority tax bill (council tax), a letter from bank, utility bills (except mobile phone bill), TV licence etc. This document has to be provided as certified copy too.

4. Bank statements
Bank statements of the last 3 months. They accept either certified copies or official digital files (pdf printed from the bank website).

PUT IN AN OFFER

The real estate market in London is extremely peculiar, property prices can change dramatically in a very short time. Before arriving to a figure you should consider:

1. The market trend
Certain periods like before elections or after the approval of regulations (like the Mortgage Market Review) are critical. Get the pulse from RICS News, The Guardian, This is Money. If the market is not going that great you have more power to negotiate the price down.

2. Your position
First time buyers, buyers with no chain and buyers who have pre-arranged mortgages are in a very favourable negotiating position, especially if the seller is in a chain (see below).

3. Vendor's position
Try to find out if they in a hurry to sell (very often the case if they are in a chain).

4. Inflated Price 
London real estate agents list prices at minimum 5-10% higher than the figure the vendor has in mind. Have an educated guess at the price the vendor wants and then pitch your own offer a bit below.

5. Repairs required
Estimate how much you will have to invest in the refurbishment/repairs.

THE AGREEMENT IN PRINCIPLE

Before looking for a property is good to know if you can apply for a mortgage and how much you can borrow.

> Foreigners are able to buy property in the UK.
> Most nationalities are eligible for investment loans, but not with all banks.
> Lenders will require proof of income and possibly to pay up to 40% deposit.
> Foreigners can often secure loans in their own country, with different tax implications.
> Expats will need to secure the services of a solicitor/conveyance solicitor in UK.
> Expats will be asked to pay 10 percent of the purchase price at exchange of contracts.

An Agreement in Principle (AIP) is a document that a lender will provide you after taking some basic information, performing a credit search and coming up with a figure that ‘in principle’ it would be able to lend.

Something to know

The easy credit boom of the 2000s played a big part in the recent UK financial crisis.
From 2012 lenders have to carry out stricter checks on borrowers: expect to be quizzed on habitual spending like your rent, energy bills, mobile phone or gym contract.

HOW TO START THE SEARCH

You actually have 3 ways to start your property search:

Estate Agency

PRO perfect if you have a particular area in mind; you deal with only one persons; they make an initial selection for you; you can build a sort of fiduciary relationship with the agent; they can combine multiple views and take you around with their car.

CONS their clients are the vendors so they don't really work in your interest; they try to sell first all the undesirable properties in their portfolio; if you are not clear from the real beginning they show you a lot of non relevant properties;

My experience with London agencies:

Foxton is the most expensive for buyers (there is no actual commission for buyers but it's well known that it's pretty much added to the property price). They have almost 40% of the properties on the market in their portfolio so sometimes it's an obligatory choice. Very polite agents.

Green and Co young and keen. Affable and not too pushy. Fresh and good service.

Pembertons No transparency whatsoever. Felt screwed over for a good 3 times. Arrogantly pushy without Foxton manners and politeness.

Faron Sutaria very professional and not insistent at all. You have the clear impression that they deal with only certain type of properties

Jorgensen Turner they tend to communicate a lot by phone or text messages, a bit 'old style' service. They deal a lot with still underdeveloped areas, like Kilburn.

KFH they tend to deal mostly with new or just refurbished properties. This reflects their type of clientele.

Marsh and Parsons they deal mainly with large and therefore relatively more expensive properties.

Barnard Marcus: they have often purpose built block and council houses properties in their portfolio.