Thanks, yes, I do have the seedphrase of course :-)
I'll try and de-/re-install this afternoon.
Then I suggest you download the latest version of Electrum here:
https://electrum.org/#downloadOnce you installed the wallet then verify its signatures
[GUIDE] How to Safely Download and Verify Electrum And follow this
1. Choose "Create a new wallet" and click "Next."
2. Select "standard wallet option" and click "Next".
3. Choose "I already have a seed".
Now your wallet will be restored successfully with all the funds in it.