Schengen to Schengen connecting flight via Gatwick UK

Hi,
Indian here flying from Iceland to Germany on Multi schengen tourist visa with connection in the UK. I will lay over for 3 hours in UK will I still need a DATV? As per exemptions in the https://www.gov.uk/check-uk-visa/y/indi ... re_else/no I should be good to go but just worried about this schengen ADS visa, whereas I have Multi schengen tourist visa...

I don't know what's the difference between ADS and just Schengen visa, I would not just assume it's fine and it's the same thing as mult Schengen visa if my transit would depend on it.
But it's irrelevant in your case - even if you'd have an exemption, you still can't go through this in transit without a visa.

Gatwick doesn't have airside transit. You have to leave the terminal and go through passport control, which you cannot do as you don't have a UK visa.
Ref: https://www.gatwickairport.com/at-the-a ... nnections/

When you arrive at London Gatwick for a connecting flight, you must pass through UK border control. Also known as a 'landside' transit.

For this (landslide transit) it's a different story even on UK visa checker.
https://www.gov.uk/check-uk-visa/y/indi ... e_else/yes

You’ll need a visa to pass through the UK in transit
You should apply for a Visitor in Transit visa if you arrive on a flight and will pass through immigration control before you leave the UK.

UPD: I looked up the ADS visa and yours is not going to cut it - ADS Schengen visas seem to be a special type of visas given to Chinese nationals traveling in groups.
https://www.swedenabroad.se/en/about-sw ... ds-groups/

An ADS visa issued by a Schengen country permits travel within the Schengen area in accordance with a pre-determined itinerary. ADS visas are issued to members of tourists groups of at least 5 persons. The maximum duration of stay is 30 days.

So you can't transit through UK at all without a visa, even if you were flying to Heathrow, which has a transit area.

Thanks @meself I have decided to ditch the stupid UK and to go through Copenhagen instead...