For what it costs to do a trade show (booth, brochures, cards, stall fee, meals, ad-specs) you could buy a great list, create some great content, pay for a year's worth of email service provider, spend £1,000 on pay per click, run a social media campaign across 2 or 3 channels and still have £1,000+ remaining for other marketing.
In some industries, trade shows can have decent ROI. For yours, I wouldn't even consider it - there's too much choice in the market, so a better approach is a PPC campaign for buy-ready low hanging fruit, repeated messaging (drip fed email nurturing for those not quite buy-ready) and multi-channel so that people see you everywhere at once.
A good portfolio, some case studies of how great design is driving results and you're cooking with gas.