What to grow?

Are you able to dig up the gravel or will you have to keep to pots?
Pots will obviously keep your new plants smaller - from your photo, it looks like you will need plants to screen you from passers by.

It looks like a really good plot - clematis is an obvious thought for the railings, you can pick and choose colour and flowering season to suit your needs. You might like to mix plants that flower in different seasons to give you blossoms all year.... remember this will cut out some of the sunshine you get in the plot.

Do you get a lot of pollution from car exhaust? If not consider a few veg and herbs in among the flowers? You might leave the gravel to deter slugs etc and make some deep wooden raised beds. Don't forget your walls, hanging basets or strong cheap plastic shopping bags in a colour of your choice, filled with compost, cut small cross to insert plants as you fill the bags, and include water retaining granules, feed with a liquid fertiliser, The plants will soon hide the bags. A sunny spot will need watering so consider putting in a planned watering system, before you start.
Flowers that do well in sun, sunflowers, climbing nasturtiums, marigold. galliarda, moss rose, periwinkle, amaranthus tricolor, sometimes known as Joseph's coat.
Veg to consider, salad leaves, tomatoes, courgettes, cucumber/ melons will grow up poles or down from a bag, peppers can look colourful. Herbs basil likes a warm spot, parsley, coriander. Strawberries/ herbs in a tower pot?

I live on a housing estate where many of the front gardens are like yours - we've got various ways of helping many grow pots of things (you have to weigh them down round here or they get nicked! - bricks in the bottoms etc) my neighbour grows bamboos for screening in pots which grow pretty quick also ipmoa - grandpa Otis is great its quick growing and flowers all summer.We use lots of hanging baskets (because they can be attached to the walls) which need not just be for flowers - I grow tumbling toms in mine, also strawberries do well - I've also seen lettuces and herbs also.
Rosemary and lavenders look stunning all year round and will definately take the sunshine. Good luck!

People are saying Clematis, which are fine ,but as you are facing south west the flowers will face the road! If you plant in pots ,a tip, use cheap pots ,scrap back the gravel ,hopefully you will have some soil under it but it will probably have a lot of builders waste, cut the bottom off the pot and plant , relace gravel around . Youwill find the pots need far less watering(always a bind !!).

How about climbing jasmines? They can be fragrant, and some are evergreen. They would make an attractive screen, and you could get varieties for different seasons . Just a thought. Clematis would grow through them, too.

Roses on the railings would be good - choose a variety that likes sun or part-shade and the flowers should face both ways! ( Rosa Madame Alfred Carriere - cream, Rosa New Dawn - pale pink, rosa Buff Beauty - peach) All could be grown n pots of necessary but - use huge pots (half barrels are good) and topdress annually as well as feed regularly. Hardy Fuchsias make good container plants or can go in ground and flower all summer long - could even be planted as a hedge along your railings, would screen you when sat but could be trimmed to required height.