The exit options for investors in private businesses are quite different from the process of buying and selling public shares. Currently, shares bought in the types of businesses that raise with Crowdcube are not typically available to trade on a secondary market, and therefore your exit options as an investor are more limited.
Investments made in private companies should be seen as longer term investments as shares are illiquid and should be viewed as longer term investments.
If an opportunity to sell your shares becomes available you will be notified either by the company directly or Crowdcube depending on your shareholding.