A visa allows you the possibility to travel to a country (not necessarily the right of entry) during a certain period of time. If you really think you can overstay by 30 days a visa, why don't the authorities issue the visa for 30 days longer. This way it would be far clearer.

Your visa allows you to stay up to 23.59hrs local time on the date of expiry. At 00.01hrs the next day, your best to be out of the country.

If you need to stay longer, get an extension in advance; the rules are really VERY logical and simple.

It will be very difficult for you now as all your details stored on computers all over Europe and in all EU (incl UK) embassies and visa issuance centers, you overstayed and that's it, your no longer considered reliable or worthy of the possibility to travel to Schengen or UK.

Tough, but that's life.