Hmm, I would say at that price you won't be in business very long.
For that price I would say there is no way you can give the attention to detail, research, design, approval, scope, service and many other things that go with this kind of work. You are realistically looking at less than 2 days to be able to create all of that without even going anywhere near maintenance or
SEO.
What if someone came along and wanted a 100 page website, you make no mention of clarifying what a Website would contain for that price.
Or they wanted a 100 page brochure, that could take weeks to create depending on the content.
How can you afford to do all this as cheap as chips, is there a typo?
Web development could mean all manner of things and you would most certainly not manage to sustain a business by charging a one off price as low as that for ongoing development.
Search Engine Optimisation - again, this work can take hours, weeks, months, effort, dedication, onsite should really be a given at a good basic level, offsite is another different beast and you would not get very far with 400 quid on its own regarding
SEO let alone in a bundle.
Don't mean to have a go here but I cannot think of how all this could be done at a price which would only run a small business for approx 1-2 days.