There is a wealth of legislation dealing with e-commerce and so-called "Information Society Services" in the UK and much of it is inspired by EU legislation.
The principal piece of e-commerce legislation in the UK is perhaps the Electronic Commerce (EC Directive) Regulations 2002 (SI 2002/2013), which implements the relevant EC Directive on the subject (ie EC Directive 2000/31). This was extended by the Electronic Commerce Directive (Miscellaneous Provisions) Regulations 2018 (SI 2018/477) to cover certain offences under UK law which were enacted after the 2002 Regulations came into effect on 21st August 2002.
The latest piece in the jigsaw is the Electronic Commerce (Amendment etc) (EU Exit) Regulations 2019 (SI 2019/87) which seeks to amend the above-mentioned 2002 and 2018 Regulations by localising their application to the UK in the event of a "no deal" Brexit.
The various Regulations between them cover (amongst other things) electronic contract formation and information requirements and the liability of service providers in the e-commerce context.
The original EC Directive is an example of the valuable work undertaken by what is now the EU and also by the wider EEA to legislate in a uniform way for borderless trade by electronic means across the multiple national jurisdictions covered by the EU and also by the wider EEA.
It will be particularly important from a trade standpoint to ensure that uniformity and ease of access is preserved as much as possible in a post-Brexit world.