Those things may not happen - they are still the easier options that don't mess up other UK sellers business though.
I've run an internet business from a small warehouse. Far, far cheaper per year than friends running a shop based business from a shop.
Small shop, 20 sq metres, £19k in rent and rates. My warehouse, 5 times bigger had less than a third of the cost.
Additional packaging and shipping costs - hopefully you are getting customers to pay that in some fashion, same way the shops get the customers to pay the staffing, utilities, business rates etc.
An extra internet tax will get treated the same way other taxes are. Passed on to the customer (higher prices) or passed on to the staff (lower pay rises / less perks).
Rarely gets passed on to the owners. They still want a profit!
Personally, I've not found an internet business that is cheaper to run than a retail shop. The costs are different. Where a shop can rely on footfall, a warehouse cannot. It needs additional marketing spend (generally, unless you're super unique and manage to crack being viral on social media or have an amazing product that walks itself out the door). Initially both options may require high marketing costs to drive footfall but a retail shop, in a good location, can safely reduce costs here. Internet businesses? No. You die if you don't do marketing.
Rent is cheaper for a warehouse, generally. That saving is absorbed by one of the other internet based costs, that a retail store, in general doesn't worry about.
Packaging costs - these are absorbed in shipping/distribution. The customer doesn't really pay them. They sit within the margin of a business. Shop costs for these tend to be lower, save for generic shopping bags. (I'm being very general about this, some shops have lovely and expensive packaging to consider).
I've found retail shops generally sell at a higher price for the same product. Less competition for the same item based on their location. However, also reduced number of sales due to reduced footfall comparable vs online. The internet is massive, the high street is not. It's impossible to compare them.
Retail shops don't have to worry about postage either. Customers will sometimes pay this, on certain large items the delivery cost will be free and the business will take the hit, to get the sale or just absorb it in the distribution costs.
Taxes - these don't always get passed on to the customer. Some businesses will absorb the cost and maintain competitive pricing. I've seen this happen consistently over the last decade or so. VAT changes - some businesses added them on for the customer to pay, others didn't and increased their market share but reduced profitability. A risk but it can work if you're flexible enough and can adjust some costs later with your improved market share.
This is why I don't like blanket taxes to solve problems. It doesn't work. Taxes are not reactive enough to situations and business life cycles. Every business is completely unique, even if it sells the same product variants. Staff numbers, warehouse costs, shop costs, packaging, postage, location - all unique.