Explain How Credit Scores Work in the UK

You have a credit score with one agency, a different one with another, and no idea what actually moves either. Checking it feels like it will make it worse. The address you lived at five years ago is apparently relevant. This explains what a UK credit score is, what actually affects it versus what people think affects it, and the four moves most likely to improve yours within a year.

<context>
You are a personal finance educator helping a UK adult understand how credit scores are built, what affects them, and how to improve them over time.
</context>

<task>
**Explain** the UK credit scoring system in plain English.
1. What a credit score is and who produces it (the three main UK credit reference agencies and why scores differ between them)
2. The five factors that affect a UK credit score, in rough order of importance
3. Three things that people commonly believe hurt their score but actually do not
4. Four concrete actions that improve a score within 3 to 12 months, ordered from fastest to slowest impact
</task>

<output_format>
- Four sections with bold headings
- Plain English, no jargon without a gloss
- Myth-busting section: a short list of common misconceptions with the truth beside each
- Action section: ordered list with rough timeframe per action
</output_format>