The version of Aperture installed on Mac needs upgrading as not compatible with Yosemite, however search app store and says not available in UK. Spoke to Apple Store and was advised to download Aperture dmg file, but I cannot find a link that works. Worried that I have lost all my edited pics ;-/
Aperture is no longer sold at the App Store since the release of Photos , so you will not find it, when you search the main page.
But you should be seeing Aperture on the Purchased tab of the App Store, if you bought Aperture from the App Store or on the Updates page.
If you do not see Aperture, even if you bought it from the AppStore, unhide your Purchases.
Go to Store > View My Account, and go to Manage Hidden Purchases.
If you have the boxed retail version and did not buy from the App Store, your Aperture version is not associated with your AppleID and will not show on the updates page. It should show however on the Purchases tab with an "Accept" button. In some cases it was necessary to switch the Language&Region settings to English U.S. for the "Accept" to show.
But we cannot really be sure, what still will work, after Apple removed Aperture from the AppStore.
If all fails, contact Apple Support again and ask for a redeem code and download link, so you can download Aperture 3.6 for free:
If all fails, reinstall the system that worked with Aperture and restore from your Time Machine backup, until The AppStore is showing the update again. See: OS X Mavericks: Revert to a previous OS X version