Walk away.
A couple of grand is peanuts compared to the amount you'll spend on the place over the lifetime of the mortgage. The reason many people feel obliged to put up with insane amounts of fraudulent and obnoxious behaviour is because they've spend a couple of grand early on and feel like they have to go through with it, come what may. Well, you don't. Simple as that.
It seems a completely perverse relationship: the more dishonest the seller, the more likely the buyers will take it. It's crackers, don't put up with it!
In this market, there are loads of places screaming for buyers, remember that. As an aside, unless you really need to buy, give it a miss. Flats especially.
PS I hope you've done your homework on the place or any other place you are considering.
- Last sold price- find out how much your seller paid for the place (sales since 1995 only):
www.zoopla.co.uk/house-prices/
- Use Firefox we browser and install Property Bee (google it), it adds a history of the listing which has useful info that you normally are prevented from seeing eg first listing date, price changes, any sales fallen through previously etc. Use it.
- For leasehold flats especially, find out about those service fees, they can easily run into over a grand a year and be over £2 depending on where you're looking at. Nuts.
Apologies if you know all this stuff already, but it bears repeating in case others do not.
In summary: don't take it. Friends of mine had a similar experience, basically the agent cottoned on to the fact that they are quite nice people and took advantage of their good nature. Eventually they called it a day and withdrew from the sale. It's still available a couple of months later (Surrey).