By Ali Lyon More than half of the UK’s mid-sized firms plan to invest at least £3m in the next five years in order to scale up their business. Fifty-one per cent of mid-sized companies, which comprise those with turnovers of between £10m and £300m and account for one in four UK jobs, will ringfence the sizeable amount of capital expenditure, a survey of business owners found. The research, which polled 500 firms, also found two-fifths of respondents plan to direct the majority of that investment within the UK, in a boost to jobs and productivity. The survey’s findings will be welcome news to w…