We have this in our medical kit. Though I can't imagine it is that different to the stuff from Asda.
In addition our kit contains:
Disposable triangular bandages
Various wound dressings from massive to tiny
Non adherent dressings for burns etc
Adhesive dressings (Plasters)
Various adhesive tapes
Medical waste bag
Cat C drugs: Loperamide Capsules (Diorrhea Treatment), Hyoscine Hydrobromide (Sea Sickness Tablets), Paracetamol, Ibuprofen, Asprin, Glyceryl Trinitrate (Angina treatment).
HypoStop Dextrose Gel
Tough cut shears
Going slightly beyond first aid we also carry:
Finger Pulse Oxymeter
Blood Pressure meter
RYA First aid at sea covers the Cat C drugs and I also have Advanced Life Support training.