Potentially unsafe electric oven / dirty kitchen

Hi, apologies in advance for the rant!

We moved into a rental property yesterday (private landlord let through an estate agents) and have a question regarding the wiring of the cooker and the general state of the place.

The cooker has a gas hob & an electric oven / grill. When I tried to get it working I could hear the gas coming through but the ignition didn't work nor did the oven / grill. I couldn't find a switch for the cooker so followed the power cord to find it was plugged into an extension cable & into a normal socket at skirting board level. Worse still, the point at which the cooker was plugged into the cable was directly underneath the stainless steel kitchen sink.

I'm no expert but this doesn't seem very safe to me! Is this in breach of regulations? If so, how should the cooker be installed safely?

Also, the house hasn't been sufficiently cleaned, the kitchen has been cosmetically cleaned but the appliances haven't been pulled out so there is food & fat remains where they are, tops of the kitchen cupboards are thick with dust & grease etc.

We don't move in properly until Monday so I'm putting off cleaning it. Am I within my rights to expect them to get the kitchen cleaned then? If they are unable to do so on Monday am i within my rights to recharge this to the agents?

Any advise on how I should how I should go back to the landlord / agent so that I don't get fobbed off will be gratefully received.