Any advice on buying glasses online?

[Trampoline]

I'm a bit miffed to see a high street chain is offering the same glasses as on the website, but online offers 25% off. I know the stores are franchises but it's annoying that they don't price match. I've had the eye test instore.
I'm considering buying online but the store won't do the measurements (varifocals). Has anyone successfully bought varifocals online? Recommendations welcome - trying to avoid spending the nearly £500 the store quoted!
Thanks!

Not varifocals but I've bought glasses online before - get the frames sent first so I can try them on, they usually have good returns policies then when I find a frame I see what's cheaper for lenses - online or specsavers.

Varifocals don't work online. You need to measure the frame on your face for the lens to work correctly (having had the frame adjusted first).
I do at least one re-test every two weeks for someone who has tried and failed.

If you're over 60, specsavers do a 20% discount.

Thanks for your replies!

You can definitely save money buying varifocals online, but they more sensitive so the measurements need to be accurate.

If you’re keeping your current frame, it’s usually easier as they can often use your existing measurements from the current lenses and just change the lenses to match the new prescription. Sometimes you can go to an independent optician and ask them to take your PD height measurements most will do it for a small fee (around £5–£10).

It’s when people guess or skip measurements that things go wrong. If the measurements are right, varifocals can work brilliantly and for a fraction of the high street cost.