Streetlife

Could you try Halfords at Tooting Bec?  And there's a bike shop just up past Fitness First at Tooting Bec but it sells pricey bikes so I don't know how cheap it would be.

More Balham than Tooting, but the guys at psubliminal on balham high road (opposite Sally Army) are good and worth the detour in my opinion.

Completely agree with MrsAmanda.  The guys in psubliminal are helpful and clearly interested in bikes.  

I live at Clapham South, bought two bikes from psubliminal, (one was stolen!)  and the guys are really nice there.  Its not part of a chain of shops either.  I think we are all in agreement!!

I use Crazy Horse Bicycles, small independent bike shop, near halfords (opposite side of the road) on Upper tooting high street (or is it balham high st?), near louisville road heading towards balham.

Owner is lovely & really knows his stuff.

http://www.crazyhorsebikeworkshop.co.uk/

If you want cheap and local with good work, try Derrick. He works from home and lives near Tooting Bec. He is super fast and efficient with great prices! His number is 07799180294. If you drop it off in the morning he will most likely have it done by late afternoon.

Yes, our household uses Derrick all the time.  He likes to keep busy and is bound to be more available and cost effective than people with shops to support.  Try him out.

I have used Crazy Horse for bike repairs. I have a fairly decent set of bike maintenance skills, so tend to use people for stuff that requires specific tool sets (Changing headsets & bottom brackets). The owner is a nice guy, and will do a good job. He is often busy, backed up with work, though.
Psubliminal (just past the Devonshire pub in Balham) are all very knowledgeable. Both businesses are independent and better than any chain stores - Don't take your bike anywhere near Halfords. They only know how to build bikes. Support your independent bike shop!

I use these guys

http://www.thelondoncycleworkshop.co.uk/

Friendly, no appointments, they do all sorts of repairs quickly and very reasonable.

I have cycling in London for over 30 years and lived in the Tooting area for nearly 25 years.    I agree with Lee B about not to use Halfords.  I use a cycle shop that does not sell bikes.  They specialise in cycle repairs and selling some cycle goods.  I have found them to be of high standard and a fair price.  They are  London Cycle Workshop can be found at 125 St. John’s Hill, SW11 1SZ 020 3441 1044.  A good website too.   I know they are not quite in your patch but are worth the journey.
I have used psubliminal who have made errors in the past such as putting the wrong size tyre on my bike.  They were not that friendly either.

There's a new shop near Sainsbury's Wandsworth. Anyone know anything about them?

I am a late cyclist in life having only taken it up in my  65th year for Ironman events and without doubt the best place "locally" is

http://www.thelondoncycleworkshop.co.uk/

They have a team of four or five guys and really know their stuff. Well worth the extra mileage and were open on a Bank Holiday.  Service was about £40 odd.  I very rarely recommend people but these guys are competent.

I had a really bad experience with Psubliminal - took my bike in to be serviced and the gears then jumped about all over the place. I took it back and they said that they wouldn't have let the bike out of the shop in that condition and I must have tampered with it. Apart from riding it, I hadn't touched it. They basically said I was lying and refused to do correct it for free. 

Hi Emmsar , the new cycle shop is the cycle surgery http://www.cyclesurgery.com/press-new-store-wandsworth/content/fcp-content , along is a runners need shop as well at the same space.

Psubliminal is my recommendation too. Avoid Halfords!

There's a great bike shop on St Johns Hill.

It looks like everyone agrees about Halfords....

http://uk.finance.yahoo.com/news/shoppers-rank-halfords-lowest-high-155745941.html