The experience and details are very useful
When buying a house/apartment, what should I look for in a viewing for red flags?
I have only bought a new built before
Are you considering a move from HK directly to buying a house in the UK? If so can I be bold enough to suggest that you consider renting for a year first? Its very risky imo to just move from overseas and immediately buy your home.
This will allow you to get to know an area and its surrounding areas. Lots of buying red flags are much more apparent only with a bit of local knowledge
Always politely enquire with the selling agent:
how long the current owner has lived there?
their reason for selling?
what are the immediate neighbours like?
wat are the seller's plans, and do they have an upward chain to negotiate? (useful to know)
Be very clear if if its a leasehold or freehold, and the implications. Enquire precisely about the service charge + ground rent for any leasehold - these can be astronomical on some fancier complexes. Some newer builds now blur the line here, with leasehold houses quite common, and even some freeholds bequeathed to having a form of service charge attached for grounds maintenance, so don't just assume that a freehold means zero servicing costs.
If buying an older home then strongly consider getting a full structural survey done (ignore the cheaper homebuyer's report). These are well worth the money, especially if you are planning to make further structural modifications to the home like an extension then you may as well pay for it up front.
Check what council and council tax band the property falls in. These can vary drastically if you are looking at a homes in one council vs another council in the next road.
If relevant, check which school catchment area it falls in. This can be a positive/negative if you have school aged children, or irrelevant if you don't.
You can enquire about local planning permissions if there are any plans for new developments to be built in the immediate area, especially if it looks like there is land locally to do so. The conveyancer should eventually highlight these, but it could be much further along in the process and throw a spanner in the works if it casts doubts upon the original decision.
And lastly, be aware that for stamp duty purposes, a First Time Buyer is classified as someone who has never own any property before in any country (not just the UK), and this needs to be true for both of you if you are buying jointly. If you don't fulfill this criteria then you will either be classfied as a home mover or a 2nd home owner with the approriate rates of stamp duty applied.