If you want to stick with what you know and not hassle with lithium ions, the Maglite ML300LX will most likely be bright enough for your needs and could be used as a club. It’s affordable and uses common D batteries. The only downside is that depending on how often you use your light, the batteries will eventually leak over time. In the UK, I’m not sure whether or not the battery manufacturers will reimburse you if that happens. In the US, Duracell will reimburse you for leakage if the battery has not expired.
https://www.amazon.co.uk/d/qca/Maglite-Torch-Matt-Finish-Handle-Waffle-29-5-cm-ML300LX/B00S7W3GDQ
The suggestions for AA lights are also good since you can use rechargeable AAs (Eneloops) and not need to worry about leakage or batteries being available. I’ve reviewed the Thorfire TK4A and like it alot. Uses 4xAAs.
If you want a super bright (2000 lumen) AA light, the Nitecore EA81 uses 8 AAs. I have this light and it is both really bright and has really long runtimes. Because it uses 8xAA, it is also heavy enough to be used as a small club. This is about the size of a 2-D Maglite. The output and runtimes of this light rival lithium-ion lights and in fact, this light will do better than most 1x18650 lights.
http://flashlight.nitecore.com/ILLUMINATION/E/EA81/
If you do want to try a lithium ion light, I would recommend a good light with built-in charging. Lexel recommended the Olight R50 Pro Seeker. However, according to the below review, the light never stops charging completely when the battery is full. So, if you get that light you must remove it from the charger when it is full or the battery may potentially be damaged over time or overheat.
The Olight R50 Seeker (non-Pro version) does not have the charge termination problem so that is probably a more fool-proof unit if you don’t want to think about needing to remove the light from the charger: