Tbh re: the oven I would get a professional in to do it.
I normally clean mine myself but prior to my last move got a company in to do it.
It took 2 hours but it was like new (inside the oven, vertical and horizontal racks, integrated baking trays etc), all the hob inc gas rings.
They had all the chemicals (more potent than you can by domestically ), soaking trays/bags, tools for fiddly areas, masks/gloves etc.
Cost me about £175 but I think I'd have spent about £60 on all the products alone.
I couldn't have done it to that standard myself to be honest even if I'd spent a day doing it.
Not cheap but money well spent (I had a large 2 oven range cooker with 6 rings and a grill top for reference).
Other tips (on house 7 here) obviously deep clean, declutter, fresh flowers in prominent places and make sure any odd jobs are done.
Finally don't forget the outside. Fresh coat of paint on the front door if needed, some nice pots, wheelie bin storage etc - kerb appeal to make people feel good before they walk in the door.