Can bailiffs take a mobility scooter parked outside?

No

A mobility scooter is an item or equipment reasonably required for the care of a disabled person or an older person and is a class of exempt goods.^[1]

When the enforcement power comes into effect, the property in all goods of the debtor, except goods that are exempt goods.^[2]

If a bailiff takes anything reasonably required for the care of a disabled person or an older person, the debtor, or the owner may may a claim to exempt goods.^[3]

^{[1] Regulation 4(1)(b)(ix) of the Taking Control of Goods Regulations 2013
[2] Paragraph 4(1) of Schedule 12 of the Tribunals, Courts and Enforcement Act 2007
[3] Civil Procedure Rule 85.8
[4] See Making a claim to exempt goods}