Quick Answer: No — by law you don’t need an IDP to drive in Malaga, Spain if you have a full UK photocard licence in English. Drivers from the UK can legally drive without an IDP. Your licence validity depends on length of stay as a visitor — in Spain that’s up to 6 months.
But — get a 1949 IDP anyway if your licence is paper, or was issued in Gibraltar / Channel Islands / Isle of Man, or you want zero hassle. Some rental desks at Malaga Airport (AGP) still ask for one and insurance can be smoother.

1. When do you NEED an IDP for Malaga?
You DON’T by Spanish law if your UK licence is photocard, in English and in date.
You DO need one if: your licence is old paper version, your licence was issued in Gibraltar, Jersey, Guernsey or Isle of Man, your hire company requires it in their T&Cs (many do), or you’re staying over 6 months / becoming resident.

2. Which IDP for Spain / Malaga?
Spain is a 1949 Convention country, not 1968 for UK permits. So you need the 1949 IDP if you need one. The 1949 type is valid for 1 year from issue.
That’s different from France / Portugal / Italy which need the 1968 IDP. If you’re driving to Portugal via Spain you may need both 1949 + 1968.

3. Where to get it?
£5.50 at PayPoint stores across the UK — not Post Offices anymore. Bring your photocard licence + passport photo. Takes 10 mins.

4. What Malaga hire companies check:
Full UK photocard (not provisional)
Passport
Credit card in driver’s name for deposit
1949 IDP if they ask — they can’t rent to you without it if their policy says so, even though Spanish law doesn’t require it for most UK drivers.

5. Malaga driving tips for UK drivers:
You will NOT feel at home — Spain drives on the right, opposite to UK. Speeds are 50km/h in towns, 90km/h single roads, 120km/h on AP-7 / A-7 motorway unless signed. Tolls on AP-7 Marbella-Estepona — pay cash/card at booth, most hire cars don’t have e-tags. ZBE low emission zone in Malaga city centre — all new hire cars are Cat C / ECO / 0 so you’re fine. Fuel is full-to-full at AGP.

For low-deposit cars, compare at cheap car hire Malaga — same £4/day comparison.