There are often items offered for free on local sites such as Freecycle, Freegle, Gumtree and Nextdoor sites. Other potential sources to consider are Facebook Marketplace, Facebook Worcestershire Waste Exchange, Worcester Resource Exchange, Worcester Council Composting and the local Transition Network.
Local garden centres often have end of season clearance sales in preparation for the following year, or you can join the Worcester Allotment & Garden Association, better known as The Allotment Shop where you are able to purchase items whilst supporting a good cause. (There is a £2/year subscription to the shop) The Shop is located on the Lansdowne Road South Allotment Site; opening hours are Tuesday, Thursday & Sunday from 10:00 am to 12:00 midday. (Although in the current COVID-19 Pandemic, the allotment shop is shut)