Urgentl need a plumber for my washing machine problem

Can someone help urgently with a problem I have whilst I'm in London. 

I have rental guests arriving at my place in Neuva anadalucia and a problem with the washing machine is flooding the kitchen sink and overflowing. 

This happened about 1 year ago ( the apartment is new, I am the first owner. It was cleared and started again in June. the apartment is not used full time so I am clueless about what may be causing this. 

I think it needs some seriously deep diagnostics and fixing. My regular plumber has not been able to fix it. 

Thanks and I stress the urgency to get it fixed ASAP. 

Harjeet