Facing the same problem. Other than holding the profits as cash I don't know what I'd do if I sold though... nothing else in the market seems as safe a bet as oil currently. But that could change quickly depending on world events...
It's the following consolidation of shares. After the B shares have been issued and redeemed your share count will drop to 76% of what you previously had. If I wanted to reduce my position in Aviva I would do it myself, because of this people will be to buy more shares to maintain the same weighting in their portfolios, likely paying commission and stamp duty...
Less than a year ago they turned down a take over at over 105 per share. Some rough media and a drop in the share price and now MSFT can come in at a lower rate and the board are more than happy to see the back of some of management... Well done MSFT, recognise a distressed company when they see one.
It's always a possibility, but you can't live in fear of it as these crashes are too difficult to time. Keep diversified in good companies, hold long term and invest regularly but within your means and all will be fine.