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I think there are too many factors to give a simple answer, so I would do as dst said, work out the numbers and stick to your plan of going away.
For most people it is hard to find times in their life when they could take 6m off. If you have that opportunity don't pass it up.
Imo un-expert opinion London prices will more or less be stable over the next 18m (provided you are in a sensible location and the property is somewhere people want to live, rather than somewhere they are prepared to compromise to). Properties outside London will see a small decline.
If you know what you are doing, the most turbulent times tend to have to greatest opportunity. But if you're not a financial guru and don't want to spend your trip studying your investments then it wouldn't be my first choice.
If you have work when you return worst case you come back and live in your place.
It's not so much that (we would be well covered) but whether house prices in London change relative to those outside London and compared to money in the bank/invested...
It was much simpler when everything was stable. ¯_(ツ)_/¯