Q: Wondering if you could help or advise me on securing self catering accommodation self-catering from Aug 19th to 23rd August, within short walking distance of La Ramblas, where activity is. There will be 5 of us.

A: You have a few options. You could stay at the Citadines ApartHotel which is actually situated on La Rambla. This is a hotel that has apartments built into it so you get the best of both worlds. 

Alternatively you could opt for a holiday apartment rental. You would need to search online for an apartment rental company. Make sure you choose a reliable apartment rental agency by following our guidelines. Link given below.
 
How to choose a reliable apartment rental company in Barcelona

August is peak season in Barcelona so I recommend you sort your accommodation out as soon as possible, or you may have difficulties finding accommodation at a reasonable price.