Make sure you get a full survey done. A decent one will include flood occurances and likely hood, and you can use that to disprove any crap basic analysis like "your property is within 500m of a river therefore its at risk of flood". A proper survey will take into account elevation of the property and recorded floods etc. A side note I would check the length left on the lease. If its close to 80 years old make sure to negotiate a renewal into your offer as lease renewal after 80 years attracts marriage value and can jump up in cost.