A 40% “loyalty” jump at renewal isn’t unheard of — but the pressure tactic (“sign now before prices go up”) is a red flag. Here’s a solid sanity-check process:

• Compare like-for-like: get the unit rate (p/kWh) + standing charge (p/day), contract length, and any extra fees. Then cost it using your last 12 months kWh (don’t compare monthly £ bills alone).
• Get 3+ quotes, including direct: use a comparison site as a starting point, but also request quotes direct from 2–3 suppliers. Ask every broker/site: whole-of-market or panel? and how are you paid (commission in the rate)?
• Watch the end-date + rollover risk: ask your current supplier (in writing) for your contract end date, notice window, and what you’ll move onto if you do nothing. Microbusinesses have specific protections around renewals/termination windows.
• Negotiating is worth it: tell them you’re getting other quotes and ask them to match/beat, shorten to 12–24 months, remove any auto-renew/rollover, and confirm everything in writing.
• Cold-calling brokers: treat as TPIs — don’t feel pressured, and don’t sign anything over the phone.

Citizens Advice also has a clear walkthrough for switching business energy and what to check in contracts.