Can a bailiff enter my porch?

Yes

Bailiffs can enter peacefully through an unlocked door, or any door, or any usual means by which entry is gained to the premises (for example, a loading bay to premises where a trade or business is carried on).^[1]

Bailiffs may not break entry through a locked door, unless the bailiff applies for separate authority to do so.^[2]

Bailiffs have a power to enter using reasonable force but this is often interpreted by bailiffs to mean getting a locksmith.^[3]

Entering through an unlocked porch is not permitted to break through a locked front door to any domestic premises, unless the bailiff is collect unpaid tax owed to HMRC,^[4] install a pre-pay gas or electric meter,^[5] or collect unpaid court fines.^[6]

In any of those circumstances, the bailiff must apply for that authority separately.^[2]

^{[1] Regulation 20(a) of the Taking Control of Goods Regulations 2013
[2] Paragraph 20 of Schedule 12 of the Tribunals, Courts and Enforcement Act 2007
[3] See Bailiffs threaten you with a locksmith
[4] Section 127 of the Finance Act 2008
[5] Section 2 of the Rights of Entry (Gas and Electricity Boards) Act 1954
[6] Paragraph 18(b) of Schedule 12 of the Tribunals Courts and Enforcement Act 2007}