GPT-5.3-Codex vs Kimi K3for everyday maths

No one can give an exact number: ISA returns aren’t fixed (markets/interest rates move), and provider fees can differ.  
A reasonable nominal estimate is to assume **2%–8% annual growth** for 10 years:  
**£10,000 → about £12,200 to £21,600** (before fees).  
For a midpoint assumption of **5% yearly growth**, it would be about **£16,300**.

No exact figure exists — it depends on what the ISA holds (cash or investments), future interest rates, market returns, and fees, none of which are knowable now.

With stated assumptions on £10,000:
- 2% growth (cautious/cash): ≈ £12,200
- 5% growth (moderate investments): ≈ £16,300
- 7% growth (strong markets): ≈ £19,700

A defensible range: roughly £12,000–£20,000 before inflation, so real spending power will be lower.