ge_mod_pictures on instagram is a local art dealer at the 'beginner's' end of the market.

Thanks again for all of your helpful suggestions. Have already popped into a couple and will be checking them all out x

Have a look at La Galleria on Garratt Lane, close to Earlsfield Station (opposite side of the road, a few doors along from the lawn mower repair shop). It’s the best picture framer in the area and he has an excellent range of modern prints and pictures.

Juliet Hall is a local artist that sells direct…
Her Insta/Facebook @JulietHallART

Yellowkorner are good for photos! And king & McGaw for prints.

This is what I do, I would love to help! I've just sent you a DM. 
 

I have found some lovely art on IG and found a Wandsworth woman who is wonderful and reasonable . I also use Painter and Hall in Pall Mall who has a decorative division called P&H - google them . They have a website . DM me if you want the name of the local artist and I will look up her IG account

How about contacting local artists . Or buying a quality print by a well known artist ... You don't always need to go through a gallery, the artist will probably only receive 50 per cent of what you pay.

Artfinder online has a huge selection of art, most of it very reasonable. 

Have you tried Wimbledon art studios? They are now selling some pieces on their website and lots of pieces for this price range. You can contact the artists if you wanted to see the pieces before you buy and best thing is you are buying straight from the artists so no commissions for galleries or so.

https://www.wimbledonartstudios.co.uk/buy-art

If you are not in a rush you can visit their next art show on May 12-15 and browse live.

Cox & Cox
Next
M&S
Amara Home
Dunelm
Wayfair
and of course Mimi in Balham:  http://www.balhamartworks.co.uk/about.html

Thanks for the replies everyone. Will check these places out. Much appreciated.

Etsy, the online marketplace, has some beautiful second-hand paintings which can be bought. Many are vintage but are in incredible condition. Worth a look.

The Wine Twit on Nightingale Lane has pictures by local artists up on the walls for sale as a sideline.  And have you tried Webbs Gallery in Webbs Road?  They have a very wide selection across a wide range of prices, certainly within the range you quote.

Have you tried Mimi V in Balham?