Terry -
As a private pilot flying out of Gamston I can assure you that we are very aware of the risks of a collision in uncontrolled airspace. Any collision would hurt us just as much as the passengers and crew of a 737 or similar.
There are reciprocal arrangements in place for light a/c operating out of Gamston to contact DSA on northerly or westerly headings as these potentially encroach on the descent patterns and approach paths for the commercial guys using DSA.
Doncaster Sheffield IFR traffic receives a Radar Advisory Service and all traffic will be vectored safely around light a/c known to DSA air traffic control. In any form of airspace, controlled or otherwise, there is a miniscule risk of collision - it is how that risk is managed that matters. At present there are insufficient aircraft movements at DSA to warrant controlled airspace (other than the ATZ around the airport itself, which requires permission from ATC to enter).
Exactly the same applies to other commercial airports in uncontrolled airspace (eg. Norwich and Humberside). I'm not aware (although stand to be corrected) of any collisions with commercial traffic at or near those airports - and they have both been operating for many years, so I would hardly say it is fair to call it 'obviously unsafe'.
The onus on VFR traffic (such as myself in a Cessna 172) is to keep the mark-one eyeball functioning and to be on a constant lookout. Together with the use of transponders (for those of us that have them) and something called 'good airmanship' we intend to preserve the safety of both ourselves as hobby pilots and those travelling to and from their holidays in the heavier metal. The last thing we need is to create unnecessary controlled airspace around every single airfield until such time as the number of a/c movements (and controller workload) warrants it.
Personally I'm delighted that DSA is operational and I hope it becomes a greater success in future years, but without the continued (relative) freedom of those of us at the grass-roots of flying, the very future of commercial aviation would be jeopardised...