[sacnoradhq]

Haven't been there in a while, but I was able to collect VAT refunds a LHR.

Is that on top of VAT?

[heimidal]

Yes, it's on top of VAT. It's usually "discretionary", meaning you can ask to have it taken off the bill, but you must ask and it usually results in being glared at.

[brewdad]

You can’t collect a VAT refund on services, only goods purchased and leaving the country. The VAT on your restaurant bill is non refundable.

[t3rabytes]

The UK is an oddball now -- VAT-free shopping for non-UK citizens ended in 2021. You can still do it in (most?) EU member states though.