Not sure if this is still on the market.
I grew up around here and have recently bought not very far away. I spent nearly 2 yrs looking (!) so know the area and market fairly well.
If I may offer some well meaning advice...
Although I love the area, I do agree with a pp that people looking to live here are not going to be interested in the Art Deco thing at all. This is an area for families, schools, and practicality, and although buyers might like a hint of period, I think this property is too extreme for this market.
I think the flat roof would put buyers off too. It put me off when I was looking and I'm an ethnic minority, so who knows, maybe the agent had a point?! 
I think it is extremely over priced - the agent has had to reduce 2 out of 6 properties in this area that were priced over the £500k mark. In this area people are expecting to pay up to £600k for a 4/5 bed and even then the standard of deco (I don't mean superficial) would have to be such that there is no work required. In contrast, the bathroom here will need replacing (I understand it's a feature, but I think buyers will just see it as 'old fashioned'). Also, the kitchen is tiny compared to the rest of the house.
Other houses in the area will boast extensions at the back, making for larger kitchens, and for less money. With pointy roofs. Sorry.
3 viewings is shocking and I do feel for you. Your agent(s) are doing a terrible job :(
I would advise that you tone down the art deco thing and post more pics of the kitchen looking as large as possible.
Also post pics of the front door as I think people like to visualise where they enter the house. Also I would remove the pic with the car and just show the front of the house with all the driveway space.
I do think you need to lower the price as well, I'm sorry but I do think the Art Deco style is actually taking value off your house for the market in this area. Good luck and I hope I'm wrong about everything and it sells today!