the Berkshire Computer Support (www.berkshirecomputersupport.co.uk) website appears to have moved to support.berkshirecomputers.co.uk, is this just a clever way of saving on domain names?

It looks like more of a strategic consolidation than just a cost-saving measure on domain registrations (which usually only cost about £10–£20 a year for .co.uk names).
Based on the current state of their sites, there are a few likely reasons for the move:
1. Brand Consolidation under "Sircles"
The parent company is sircles.net Ltd, and they have been operating several different "Berkshire" branded domains (like berkshirecomputersupport.co.uk, berkshire-computers.co.uk, and berkshirecomputers.co.uk). By moving to support.berkshirecomputers.co.uk, they are likely trying to create a single "master" domain for their computer sales/recycling and using the subdomain ("support.") to organize their service wing.
2. Infrastructure & SEO
Moving a legacy site like berkshirecomputersupport.co.uk (which has been around for over 10 years) to a subdomain of their main brand helps "pool" their Google search authority. Instead of having five small websites competing with each other for "computer repair Berkshire," they have one large website that looks more authoritative to search engines.
3. "The Shop" vs. "The Service"
The new structure seems to distinguish between their different business arms:
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The Main Domain: General business and computer recycling.
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The Subdomain (support.): The technical help desk, Mac repairs, and data recovery.
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The Store (store.sircles.net): Where they actually sell the refurbished hardware.
4. Avoiding "Striking Off" Confusion
Interestingly, there was a separate entity called Berkshire Computers Limited (incorporated in 2023 at the same Winnersh address) that currently has an "active proposal to strike off" according to Companies House. By moving the website to a subdomain clearly owned by sircles.net Ltd, the owners (Simon Cooper and Ferenc Gerencser) may be tidying up the digital presence to ensure it is clearly linked to the stable, long-running parent company rather than the newer, potentially redundant limited company.
So, while it does save them from managing multiple separate web hosting plans, it’s mostly a move to make their sprawling network of "Berkshire" domains easier to manage and find.