Usually yes! Whilst you need to be careful with claiming food costs, as it can be difficult to prove that they are wholly and exclusively for business (given you need to eat to survive), HMRC has a term called itinerant in nature.
Itinerant means to travel from place to place and in this context refers to your business requiring you to be constantly travelling to conduct your trade.
This means that a plumber or builder can indeed claim the cost of their lunch while travelling from place to place in the course of conducting their day-to-day business.
You need to make sure that you keep the receipts for these costs otherwise you cannot claim the VAT and your corporation or income tax will be restricted to HMRC's fixed rate subsistence deductions.
Get in touch if you need the support of Accounting Experts that specialise in these types of businesses.