Planning appeals to the Planning Inspectorate can take significantly longer to be processed than a simple planning application. The total timeframe can be highly variable, but typically you can expect to be waiting for months. From January 2016 to December 2020, the mean planning appeal waiting time was 26 weeks.
A planning appeal can be submitted by written representation (the most common way), a hearing (typically for when there is a public interest in your proposed development), and for the most complicated cases, via inquiry. Depending on the nature of your appeal, you may be better compromising with the LPA on some conditions if time is tight.