How helpful is forwarding your CV really for getting a Summer Analyst position?

I'm still at uni and will apply for SA positions in the UK soon. By having family members working in the industry, I will be able to get in touch with people from several firms but I am wondering and not sure about how helpful such contacts actually are. Is the conversion rate of people just getting their CV forwarded on average actually so much higher than of those that do not have a connection and are applying through the normal online application channel? To those already having completed a SA programme, was the portion of participants that had a contact at the firm really that unnaturally large?