A security issue needs fixing on my site. Written in ASP

Actually I have just been told it is ASP. net but cannot edit the title.I have a 'comments' section on my blog on my website. All the posts get spammed and my server recently stopped hosting my site because of the amount of 'dangerous submissions'. I have now removed them all but will attach an example of the kind of thing that happens. I want this to stop happening. Please can i have a quote if possible and details of what you can do. Thankyou.
I would ideally like someone who is based in Bath or Bristol and who does not add on VAT