Comparing apples and oranges. The HSF plans are for outpatient benefits whilst the plans by the 3 insurers are for inpatient benefits plus outpatient benefits - the level of outpatient benefits is dependent on plan chosen.
The Smart plan from Aviva was designed to complement the benefits under the HSF plan but the price is both can be beaten by all 3 insurers.
VHI have cheaper options without having to reduce inpatient benefits whilst maintaining outpatient benefits.
Ask them for their best plan that suits all your needs and post your results here.
Think long and hard about giving up your inpatient cover.