Depends what you want to achieve Miss24... and what you are currently using. There is a lot of noise this time of year about "winter waxes" and the truth of it is unless you are using a boutique wax thats designed for the show field to give maximum looks with low durability anything will be fine over winter. The only difference is that some waxes are designed with durability in mind so people think they ought to swap over to a more durable wax during winter... it only makes a difference if like i said, you use products in fine weather which dont offer any real long term protection to the paint.
Colli 476s is probably the best wax under £20 where durability is concerned but (as i've said before) for me it doesnt add anything to the finish other than a durable coat - i dont rate the looks it gives.
You could do a lot worse than Zaino Z2 - 2-3 layers will see you right for at least 5 months. Without ZFX (looking at the Zaino range will explain everything) you cant layer Z2 in a single day (due to the curing times) but you could layer it over a couple of days without any problems and a rinse down between days. Adding Z6 to wipe down between layers also adds a lovely gloss to the paint.
I use Zaino all year round. Apply 3-6 layers of Z2 once every 6 months when i also
review the condition of the paint and correct it if required. During the summer if i fancy using a wax i will clean the car and then add a layer or 2 of whatever takes my fancy at the time. The Zaino is still there underneath and continues to protect the car once the wax fades away.
If you're happy with waxing though and happy to spend a few more ££'s then something like Britemax Vantage or Chemical Guys 50/50 are good waxes for around £40 - 2 or 3 layers (with an hour between) will see you right for 4 months easy.
HTH, Nige