First off, this is your new bible: https://amazingribs.com/

And this man is your new hero: https://franklinbbq.com/about

I want a grill (99% this is you)

Buy one of these: https://www.wowbbq.co.uk/categories/weber-barbecues/weber-charcoal-bbqs/weber-mastertouch

I want a smoker

Buy this:

https://www.wowbbq.co.uk/categories/weber-barbecues/weber-smokers/product/weber-smokey-mountain-cooker-57cm-and-cover/731004~731004

Burn this on it: https://www.wowbbq.co.uk/product/aussie-heat-beads-4kg-4x-4kg-bags-/1009X4~1009X4

And if you want some smoking wood, see below.

And buy these:

https://www.amazon.co.uk/Eco-Blaze-EBFL-L-Natural-Firelighters/dp/B07CQSP9XV/ref=sr_1_2_sspa

https://www.amazon.co.uk/Weber-7416-Chimney-Starter/dp/B000WEOQV8/ref=sr_1_2_sspa

https://www.amazon.co.uk/Inkbird-Bluetooth-Thermometer-Temperature-bluetooth/dp/B06WGMDSBL/ref=sr_1_22

https://www.amazon.co.uk/SuperFast-Thermapen-Professional-Thermometer-Sherbert/dp/B076DGSTQB/ref=sr_1_5

https://www.amazon.co.uk/Grillaholics-Barbecue-Accessories-Healthier-Stainless/dp/B01J6QN8QQ/ref=sr_1_4

"I've bought a cheap BBQ from Argos/Tesco/etc. Can I..."

Probably not. They are good for hot and fast grilling, and will probably last a year or two if they live outside. But they'll struggle to hold temperature, and they'll burn a lot more fuel than a thicker-skinned grill.

"Can I smoke on my grill?"

Maybe. The important thing about smoking is airflow - you've got to have it. Put simply, there needs to be an intake and an exhaust, and the exhaust has to be higher than the intake (unless you're using forced induction, ie. a fan).

You'll also need some smoking wood - this can be pretty expensive if you don't buy in bulk, but eBay have some nice bundles, something like this: https://www.ebay.co.uk/itm/Off-Set-Smoker-Wood-Wood-Chunks-14-Kg-smoking-Wood-Apple-oak-cherry-whiskey-Ba/303438694553?hash=item46a65b0899:g:pGgAAOSwAx9b~Z6U Otherwise, order 1m³ of wood from your friendly local wood stockist. Make sure you tell them it's for cooking!