Quick answer

Window replacement cost depends on size, style, glazing, access, and how much prep work is needed. Most quotes only make sense when they are truly like-for-like.

What affects the price most

Window size and style (casement, sash, tilt and turn, bay)
Frame material (uPVC, aluminium, timber)
Glazing spec (double vs triple, acoustic, laminated safety glass)
Trickle vents and compliance requirements
Access and fitting complexity (scaffolding, awkward openings, making good)
Colour and finish (foils, dual colour)

Typical cost ranges

These are broad ranges to help you sense-check quotes. A proper survey is the only way to price accurately.

uPVC casement windows: usually the most cost-effective
Aluminium windows: typically higher due to material and fabrication
Bay windows and large openings: can rise quickly due to structure and labour

How to compare quotes properly

When you get multiple quotes, check:

Same frame material and colour
Same glazing spec and energy rating
Same number of openers
Any remedial work included (sills, trims, making good)
Lead times, guarantees, and aftercare

Next step

If you want an accurate price, book a quick survey and ask for a written breakdown so you know exactly what you are paying for.