Thanks. I must be doing something wrong.
Tried this but it strips off the html.
BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//VueSoft//CsvToIcs//EN
X-WR-CALNAME:Breakfast List2018
X-WR-RELCALID:fb31c683-823e-46e4-9ae9-5a9246522e4f
X-WR-TIMEZONE:UTC
BEGIN:VTIMEZONE
TZID:GMT Standard Time
BEGIN:STANDARD
DTSTART:20171002T020000
RRULE:FREQ=YEARLY;BYDAY=-1SU;BYHOUR=2;BYMINUTE=0;BYMONTH=10
TZNAME:GMT Standard Time
TZOFFSETFROM:+0100
TZOFFSETTO:+0000
END:STANDARD
BEGIN

AYLIGHT
DTSTART:20170301T010000
RRULE:FREQ=YEARLY;BYDAY=-1SU;BYHOUR=1;BYMINUTE=0;BYMONTH=3
TZNAME:GMT Daylight Time
TZOFFSETFROM:+0000
TZOFFSETTO:+0100
END

AYLIGHT
END:VTIMEZONE
BEGIN:VEVENT
CATEGORIES:Breakfast
DESCRIPTION:Edwards's Breakfast
X-ALT-DESC;FMTTYPE=text/html:<iframe src="
https://www.google.com/maps/embed?pb=!1m18!1m12!1m3!1d2483.591905347834!2d-0.1477576843916311!3d51.5023559796343!2m3!1f0!2f0!3f0!3m2!1i1024!2i768!4f13.1!3m3!1m2!1s0x0%3A0x0!2zNTHCsDMwJzA4LjUiTiAwwrAwOCc0NC4xIlc!5e0!3m2!1sen!2suk!4v1516292773374" width="600" height="450" frameborder="0" style="border:0" allowfullscreen></iframe>
DTEND:20180617T110000
DTSTAMP:20180107T015320Z
DTSTART:20180617T090000
GEO:51.502356;-0.145569
LOCATION:Constitution Hill, SW1A 1AA
PRIORITY:0
SEQUENCE:0
STATUS:Confirmed
SUMMARY:Graham Edwards
UID:0c2c979e-1f64-460c-986f-6c038afac456
END:VEVENT
END:VCALENDAR