No intent to penalise contractor but wish to ensure we don’t trigger opportunity for claim for loss and expense, uplift in prelims etc
How do you expect to be able to stop Works on site indefinitely and it to not have an impact on the Contractor if you also don’t want to be liable for loss and expense and prelims etc? Your actions will hinder their progress, potentially increase their costs and delay them beyond the Completion Date which will make them liable to pay you LADs!
If you want to limit your liability then leave the Contractor to get on with the Works and let them make their own decision about whether to carry on or not. This way you might avoid loss and expense however you will still likely be liable to give an extension of time.
If you want to intervene then the only contractual procedure is at clause 3.15 (SBC) and to issue an instruction to postpone the Works which could lead to both an extension of time and loss and expense. Given the grave circumstances in which we all find ourselves I find it morally questionable that any Employer would seek to do anything else.
You are of course free to negotiate with the Contractor and enter into a settlement / compromise agreement to limit your liability however given the unknowns surrounding coronavirus your Contractor will no doubt be reluctant to consider this.