Inventory Effect

Hi,
Not exactly sure what you exactly mean?
But my initial thoughts are as follows:-

Sell the widget as a purchase item then the inventory would look after the stock etc.  Sell the service plan as a service item.

This is based on:-

The widget is sold for >£0, ie the widget is not given away @ zero cost to the client.

Yes, that makes sense now...

So as previously mentioned 'Sell the widget as a purchase item for $44.99 then the inventory would look after the stock etc.  Sell the service plan as a service item for $45' which can both go on the same sales order. Use sales pricing to set the costs.

Or as you suggest a sales kit; a sales kit can comprise of 'mixed' items - so purchased items and service items can be in the same kit. The inventory would still manage the physical stock of the purchased item. Once you've created the kit use sales pricing to set the cost. But sales kit price allocation will not give you the desired sales price of the widget.

A sales kit would be less work when creating the sales order and less complicated for users, but separate items give more flexibility.

Setting up a 'training company' will allow you to test, trial, etc