So go for the BT Business package - the 4G dongle is supplied at day 1.
Also, having a "Business Package" makes it a lot easier to put the cost through your accounts and recover VAT. In my case the Business Broadband was delivered over a residential line and the accountant advised not to charge the line rental as a business expense even though it was essential for a business service. Moved the line to Business which became cheaper and also allow recovery of VAT and the rental as an expense. There are no chargeable outgoing personal calls made on te line.
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