I also use https://spanishtaxforms.co.uk/ the fee of £34.95 is for the property not per person. The company has been going for many years and I find them very efficient, there’s even a freephone number should you wish to speak to them. If you want them to pay the tax for you,it’s an extra £12 per person. I just have them send mine to me and pay it at the bank when I come over to Spain. They will email or post the completed Modelo 210 to you.
I used to do my own and it’s quite easy to do, there’s plenty of information on how to do it on the forum.
Regards
Anne