Former BUPA employee here and I just wanted to point out that Essential would be a lower level of cover than Plan B. Essential would be more similar to VHI's Plan A or Plan A Options.
If you wanted similar to Plan B (i.e. private room in public hospital, semi private room in private hospital), then you probably should look at Essential Plus.
Please note that I only say this so that you're aware of the difference in hospital cover, I'm not trying to sell their cover or anything. That's also why I won't comment on the service being better or worse, I'm biased!
You can get more info on the Health Insurance Authority's website - www.hia.ie.
Regarding the tax relief on the premium for your partner and son, assuming you pay this yourself out of your own pocket, the tax relief is given at source (i.e. deducted from the premium so you pay the net balance). This should be the same as what you have at the moment with VHI.
I have Quinn Essential Plus ( No I/P Excess )and suffered a football injury one month after beginning my cover.
I had a surgical procedure ( day care semi-private room in private hospital), and MRI, bone scan, X-Ray and cortizone injection ( All Mater Private ) all of which were either covered directly or reimbursed promptly by Quinn.
I found customer service staff to be helpful with regard to information on my cover as well as Quinn being very prompt in dealing with my subsequent claims.
Can't fault them for customer service.