The translation of asesoria is consultant or advisor.
First of all, I must tell you that there is a whole host of different types of asesoria, each dealing with different things. Here's a list:
Asesoramiento fiscal - tax advice
Asesoria civil y mercantil - civil and commercial advice
Asesoria contable - accounting advice
Asesoria de empresa - business advice
Asesoria economica - financial advice
Asesoria financiera - financial advice
Asesoria inmobilaria - real estate
Asesoria juridica - Law Office
Asesoria y gestion comercial - management and business advice
Asesoria gestion laboral - management and work
The one I mentioned on the main "Law" page was the first one - fiscal. Advice on tax matters means that this particular asesor is what amounts to an accountant, or financial advisor. You can see that the third one on the list is also concerned with accounting, so you could choose either to deal with your accounts and to work out your tax.
Like everything else, you'd obviously prefer to deal with an asesor who can speak English. I've trawled the Internet and come up with the following.
Samuel Nevado
Found in the Madrid Building, on Calle San Francisco de Paula in Santa Cruz. This is an asesoria fiscal y contable and languages spoken are Spanish and English.